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A COMPLETE TREATISE 



ELECTRO-DEPOSITION OF METALS 



A COMPLETE TREATISE 



ELECTRO-DEPOSITION OF METALS. 



COMPRISING 

ELECTRO-PLATING AND GALYANOPLASTIC OPERATIONS, THE DEPOSITION 

OF METALS BY THE CONTACT AND IMMERSION PROCESSES, 

THE COLORING OE METALS, THE METHODS OF 

GRINDING AND POLISHING, 

AS WELL AS 

DESCRIPTIONS OF THE ELECTRIC ELEMENTS, DYNAMO-ELECTRIC MACHINES, 

THERMO-PILES, AND OF THE MATERIALS AND PROCESSES 

USED IN EVERY DEPARTMENT OF THE ART. 

translated from tije" german of 
Dr. GEOKGe'lANGBEIN, 

PROPRIETOR OF A MANUFACTORY FOR CHEMICAL PRODUCTS, MACHINES, APPARATUS, 
AND UTENSILS FOR ELECTROPLATERS AND OF AN ELECTRO-PLATING 
^ ESTABLISHMENT, IN LEIPZIG. 









WITH ADDITIONS BY 



WILLIAM T. BKAOTSTT, 

I if; R 1891 

EDITOR OF " THE TECHNO-CHEMICAL RECEIPT BOOK." 

ILL USTRA TED B T ONE HTTND BED AND TWENTY-FIVE ENGBA VINGS. 



PHILADELPHIA : 
HENRY CAREY BAIRD & CO., 

INDUSTRIAL PUBLISHERS, BOOKSELLERS, AND IMPORTERS, 
810 WALNUT STREET. 

LONDON : 

SAMPSON LOW, MARSTON & CO., Limited, 

ST. DUNSTAN'S HOUSE, FETTER LANE, FLEET STREET. 

1891. 



^ 



\« 



Copyright by 

HENRY CAREY BAIRD & CO. 

1891. 






Printed at the COLLINS PRINTING HOUSE, 

705 Jayne Street, 

Philadelphia, U. S. A. 



& 



PREFACE 



The art of the electro-deposition of metals has during recent 
years attained such a high degree of development, that it was felt 
that a comprehensive and complete treatise was needed to represent 
the present advanced state of this important industry. In further- 
ance of this object, a translation of Dr. George Langbein's work, 
Vollstaendiges Handbuch der Galvanischen Metall-Niederschlaege, 
is presented to the English reading public with the full confidence 
that it will not only fill a useful place in technical literature, but 
will also prove a ready book of reference and a practical guide for 
the workshop. In fact, it is especially intended for the practical 
workman, wherein he can find advice and information regarding 
the treatment of the objects while in the bath, as well as before 
and after electro-plating. The author, Dr. George Langbein, is 
himself a master of the art, being the proprietor of an extensive 
electro-plating establishment combined with a manufactory of chem- 
ical products, machinery and apparatus used in the industry. 

The results yielded by the modern dynamo-electric machines, to 
which the great advance in the electro-plating art is largely due, are 
in every respect satisfactory, and the more so since the need of 
accurate, and at the same time handy, measuring instruments has 
also been supplied. With the assistance of such measuring instru- 
ments, the establishment of fixed rules regarding the current-condi- 
tions for a galvanic bath has become possible, so that good results 
are guaranteed" from the start. While formerly the electro-plater 
had to determine the proper current-strength for the depositions in 



VI PKEFACE. 

an empirical manner, by time-consuming experiments, to-day, by 
duly observing the determined conditions and provided with well- 
working measuring instruments, he can at once produce beautiful 
and suitable deposits of the various metals. 

The data referring to these current-conditions, according to mea- 
surements by Dr. Langbein, are given as completely as possible, 
while for the various baths, only formulae yielding entirely reliable 
results have been selected To most of the baths a brief review of 
their mode of action and of their advantages for certain uses is 
added, thus enabling the operator to select the bath most suita- 
ble for his special purpose. To the few formulae, which have not 
been tested, a note to that effect is in each case appended, and they 
are only given with due reserve. 

To render the work as useful as possible, the most suitable for- 
mulae for plating by contact and immersion, as well as the best 
methods for coloring the metals, and the characteristic properties of 
the chemicals used in the industry, are given. However, the pre- 
paration of the chemicals has been omitted, since they can be pro- 
cured at much less expense from chemical works than it would be 
possible for the electro-plater to make them in small quantities, 
even if he possessed the necessary apparatus and the required 
knowledge of chemistry and skill in experimenting. 

It is hoped that the additions made here and there by the trans- 
lator, as well as the chapter on " Apparatus and Instruments," and 
that of " Useful Tables," added by him, may contribute to the use- 
fulness of the treatise. 

Finally, it remains only to be stated that the publishers have 
spared no expense in the proper illustration and the mechanical 
production of the book ; and, as is their universal practice, have 
caused it to be provided with a copious table of contents, and a 
very full index, which will add additional value by rendering any 
subject in it easy and prompt of reference. 

W. T. B. 

Philadelphia, July 1, 1891. 



CONTENTS. 



i. 

GENERAL HISTORICAL PART. 
CHAPTER I. 

HISTORICAL REVIEW OF ELECTRO-METALLURGY. 



PAGE 



The method of coating metals by simple immersion known to Zozimus 
and Paracelsus; Luigi Galvani's discovery of the electric contact- 
current, in 17 89 ; Alexander Volta's discovery, in 1799, of the true 
causes of the electric contact-current . . . . » .17 

Erroneous inference drawn by Galvani from his experiments ; General 
ignorance in regard to the nature of the electric current ; Construc- 
tion of the pile of Volta or the voltaic pile ; Cruikshank's trough 
battery; Decomposition of water by Nicholson and Carlisle, 1800; 
Wollaston's observation, 1801 . . . . . . .18 

Cruikshank's investigations, 1803 ; Brugnatelli's experiments in electro- 
gilding, 1805 ; Sir Humphry Davy's discovery of the metals potas- 
sium and sodium, 1807 ; Prof. Oersted's discovery, 1820 ; Ohm's dis- 
covery, in 1827, of the law named after him . . . . .19 

Faraday's discovery, in 1831, of electric induction; First electro- 
magnetic induction machine constructed by Pixii ; Faraday's electro- 
lytic law laid down and proved in 1833; Production of iridescent 
colors, in 1826, by Nobili ; Production of the amalgams of potassium 
and sodium, in 1835, by Bird ; Discovery of the galvano-plastic pro- 
cess, in 1838, by Prof. Jacobi ; Claims of priority of invention by 

Mr. T. Spencer and Mr. C. J. Jordan 20 

Labors of the Elkingtons and of de Ruolz ; Murray's discovery, in 
1840, of black-leading; Introduction of gutta-percha by Dr. Mont- 
gomery, in 1843 ; First employment, in 1840, of alkaline cyanides 
by Wright; Patent for the deposition of nickel, 1840; Origination 
of the term "electro-metallurgy" by Mr. Alfred Smee, 1841 ; Prof. 
Boettger's discovery, in 1842, of depositions of nickel from its double 
salt ........;... 21 



Vlll CONTENTS. 



First deposition, in 1842, of metallic alloys by de Ruolz ; First use of 
thermo-electricity, in 1843, by Moses Poole; Advances in the art of 
electro- deposition ; Attempts, since 1854, by Christofle & Co., to re- 
place their batteries by magneto-electrical machines ; The Alliance 
machine; Objections to Wilde's machine; Dr. Antonie Pacinotti's 
invention, in 1860, of the ring named after him .... 22 

Siemens's dynamo-machine, 1866 ; Wheatstone's dynamo-machine, 
1867 ; Introduction of Zenobe Gramme's machine, in 1871 ; Hefner- 
Alteneck's machine, 1872; Siemens & Halske's machine, 1874; S. 
Schuckert's machine, 1874; Various dynamo-electrical machines; 
Investigators and practitioners who have contributed to the improve- 
ment of the electro-chemical process and the perfection of galvano- 
plasty 23 



II. 

THEORETICAL PART. 
CHAPTER II. 

MAGNETISM AND ELECTRICITY. 

1. Magnetism. 

Loadstone or magnetic iron ore ; Natural and artificial magnets ; 
Definitions of the magnetic poles and of the neutral line or neutral 
zone, and their positions . . . . . . .24 

Magnetic meridian ; North and south poles ; Phenomena of attraction 
and repulsion ; Ampere's theory ....... 25 

Definition of the magnetic field . . . . . . . .26 

2. Electricity. 

Definition of idioelectrics and of non-electrics ; Gray's discovery, 1727; 
Good and bad conductors ; The electroscope and its use ; Existence 
of two kinds of electricity ........ 26 

Vitreous or positive, and resinous or negative electricity; Symer's 
theory of the electric agent ; Franklin's one-fluid theory ; Coulomb's 
law ; Contact-electricity . . . . . . . .27 

Series of tension ; Production of electricity by the contact of metals 
and fluids ; Galvanic or hydroelectric current ; Galvanic element or 
galvanic chain ; Electrical potential ...... 28 

Electro-motive force ; Resistance ; Conductivity of metals according to 
Lazere Weiler 29 



CONTENTS. IX 

PAGE 

Quantity of current — Ohm's law; Essential or internal resistance, and 
non-essential or external resistance ...... 30 

Coupling of the elements ......... 31 

Coupling of the elements for tension and for quantity of current . . 32 
Mixed coupling; Proposition deduced from Ohm's law ; Effects of the 
electric current . .33 

Electro-Magnetism. 

Rule for determining the direction which the magnetic needle will as- 
sume when placed in any particular position to the conducting wire . 33 

Galvanoscopes, galvanometers, or multipliers ; Astatic galvanometer ; 
Tangent galvanometer ; Sine galvanometer ..... 34 

Electro-magnets ; Solenoid ; Law of the action of two electrified wires 
on each other .......... 35 

Induction. 

What is understood by induction . . . . . . .35 

Primary or inductive current ; Secondary or induced current . . 36 
Alternate currents ; Extra currents . . . . . . .37 

Chemical Actions of the Electrical Current — Electrolysis. 

Reduction of the constituents of a fluid by the electric current ; Pure 
water a bad conductor ; Faraday's discovery of the chemical actions 
of the current . . . . . . . . . .37 

Electrolysis ; Electrolyte ; Electrodes ; Anode ; Cathode ; Ions ; An- 
ions ; Cations ; Atoms ; Claussius's theory of molecular charges . 38 

Counter or polarizing current ; Faraday's electrolytic laws ; Experi- 
ment with the voltameter . . . . . . . .39 

Electrical equivalent ; Definition of local action ; Electro-chemical 
equivalents ........... 40 

Joule's law ; Consumption of power in the electrolysis ; Electric units 
adopted by the International Congress of 1881 .... 41 

Fundamental or C. G. S. (centimetre-gramme-second) system ; Force 
or power ; Work ; Quantity ; Potential or electromotive force ; Re- 
sistance ; The ohm ; The ampere ; The volt ; The farad ; The cou- 
lomb 42 

The watt ; Definition of the English and of the French horse-power . 43 



CONTENTS. 



III. 

SOUKCES OF CURRENT. 
CHAPTER III. 

GALVANIC ELEMENTS — THERMOPILES — MAGNETO- AND 
DYNAMO-ELECTRIC MACHINES. 

A. Galvanic Elements. 

page 
Voltaic pile ; Trough battery . . . . . . . .44 

Reduction of local action in elements by amalgamating the zinc ; Various 

methods of amalgamating ; Bouant's recommendation ... 45 
Definition and cause of polarization ; Smee's element 4G 

Constant elements ; Daniell's element . . . . . .47 

Meidinger element ; Grove element ....... 48 

Bunsen elements . . . . . . . . . .49 

Location of elements . . . . . . . .50 

A. Dupre's substitutes for sulphuric and nitric acids for filling elements ; 

Manipulation of Bunsen elements . . . . . . .51 

Advisability of having a duplicate set of porous clay cells ; Renewal of 

the acids . . . . . . . . . . .52 

Leclanche element ; Lallande and Chaperon element .... 53 

Various elements ; Dun's potash element ...... 54 

Dipping or bichromate batteries; Fein's bichromate battery; Keiser 

& Schmidt's bichromate battery ....... 55 

Bichromate element for gilding or silvering small articles . . .56 

Stoehrer's battery . . . . . . . . . .57 



B. Thermo-piles. 
Seebeck's discovery, 1823 ; Noe'spile; Clamond's thermo-pile . 

C. Magneto- and Dynamo-Electric Machines. 

Faraday's discovery in 1831 

Magnetic field or the region of the lines of force ; What a magneto- 
electric or dynamo-electric machine actually is ; Pixii's electrical ma- 
chine, 1832; Saxton and Clarke's improvements . 

Dr. W. Siemens's improvement, 1857; Pacinotti's ring conductor; 
Dr. W. Siemens' and Sir C. Wheatstone's discovery; Transition of 
the magneto-electric machine to the dynamo machine 

Continuous current machine and alternate current machine ; Gramme 
machine and armature ......... 



58 



5!> 



60 



61 



CONTENTS. XI 

PAGE 

Modern Gramme dynamo for galvanoplastic purposes .... 64 

Disadvantage of the Gramme machine; S. Schuckert's flat ring ma- 
chine . ... . . . . . . . . .65 

Fein's dynamo machine; Brush's dynamo and armature ... 66 
Siemens & Halske's magneto-electric machine ..... 68 

Siemens & Halske's dynamo-electric machine; Weston's dynamo ma- 
chine . . . . . . . . . . . . 69 

Kroettlinger's dynamo machine ........ 70 

Lahmeyer dynamo . . . . . . . . . .71 

Other dynamo machines ; Value of the dynamo and its effect upon the 
electro-plating industry ......... 73 



IV. 

PRACTICAL PART. 
CHAPTER IV. 

ARRANGEMENT OF ELECTRO-PLATING ESTABLISHMENTS IN GENERAL. 

Necessity of sufficient light and thorough ventilation .... 75 
Location of Bunsen elements ; Provision for heating . . . .76 
Great importance of a good supply of water ; Best material for floors ; 

Size of the operating room . . . . . . . .77 

Grinding and polishing rooms ; Prevention of dust in the polishing 

rooms ; Location of the transmission carrying the belt pulleys . 78 

Electro-Plating Arrangements in Particular. 

What the actual electro-plating plant consists of; Arrangement with 

elements; Choice of coupling of the elements . . . .79 

Proportion of the effective zinc surface of the elements to that of the 

anodes and articles ; Coupling of elements for solid and thin deposits 80 
Auxiliary apparatuses . . . . . . . . .81 

Current regulator, resistance board or switch board ; Conditions upon 

which the action of the resistance board is based .... 82 

Galvanometers ........... 83 

Location of the resistance board and galvanometer ; Indications by the 

galvanometer .......... 84 

Counter current .......... 86 

Rules to be observed in conducting the current ; Positive or anode wire ; 

Negative or object wire ; Vats for baths ; Wooden vats. . . 87 



Xll CONTENTS. 



Vats of bricks, enamelled iron, and stoneware ; Conducting rods ; 

Anodes and their arrangements ....... 88 

Various forms of binding screws ; Mode of suspending the anodes in 

the bath 89 

Mode of suspending the objects in the bath ; Protection of the rods ; 

Cleansing and rinsing apparatuses ; Dipping or pickling . . 90 

Sawdust ; Arrangement with dynamo-electric machines ; Rules for 

setting up and running dynamo-electric machines . . . .91 

Insulation of the object and anode wires ; Wire carriers ; Resistance 

boards or current regulators ........ 92 

Resistance board of the dynamo ; Amperemeter or ammetre ; Volt- 
meter ............ 93 

Coupling of the main object wire and the main anode wire with the 

resistance boards, the voltmeter, the shunt, and the baths . . 95 
Feeding the baths ; Ground plan of an electro- plating establishment . 97 
Lye kettle ; Various means of removing grease and dirt . . .99 
Table for freeing articles from grease . . . . . .100 

Mode of calculating the. thickness of the conducting wires for dynamos 101 

CHAPTER V. 

TREATMENT OF THE METALLIC ARTICLES, 

A. Mechanical Treatment. 

Treatment before electro-plating ; Scratch-brushing ; Various forms of 
scratch-brushes . . . . . . . . . .102 

Treatment of scratch-brushes ........ 103 

Circular scratch-brushes and their construction . . . . .104 

Cleansing by the sand blast ..... .105 

Tumbling drum or box . . . . . . . .106 

Grinding; Grinding disks . . . . . . .. .107 

Treatment of the grinding disks . . . . . . .108 

Vienna lime ; Grinding lathes . . . . . . .109 

Execution of grinding ; Fibres and fibre brushes . . . .110 

Grinding of iron and steel articles, brass and copper castings, sheets of 
brass, German silver, and copper-zinc castings . . . .111 

Polishing sheet zinc ; Polishing ; Foot lathe for polishing ; American 
double polishing lathes . . . . . . . . .112 

Polishing materials ; Rouge composition ; Burnishing ; Mechanical 
treatment during and after the electro-plating process ; Scratch- 
brushing the depositions . . . . . . . .114 

Effect of scratch-brushing ; Decoctions used in scratch-brushing ; Man- 
ner of executing scratch-brushing by hand . . . . .115 

Lathe brush 116 



CONTENTS. Xlll 

PAGB 

Cleansing and drying the polished objects ; Sawdust for drying the 
objects ; Drying of iron and steel objects ; Removal of moisture 
from the pores of nickeled iron objects ; Polishing of deposits of 
nickel, copper and brass, tin . . . . . . . .117 

Polishing deposits of gold, silver, and platinum ; Operation of burnish- 



ing 



a 1 



Various shapes of burnishes . . . . •. . .118 

B. Chemical Treatment. 

Pickling; Mixture for pickling cast-iron and wrought-iron objects; 

Excellent pickle for iron ; To cleanse badly rusted iron objects . 119 

Duration of pickling ; Pickling zinc objects ; Cleaning and brighten- 
ing copper, brass, bronze, tombac and German silver; Preliminary 
pickle; Bright-dipping bath . . . . . . . .120 

Use of potassium cyanide for pickling ; Storing of pickles ; Manipula- 
tion of pickled objects ; Dead dip . . . . . . .121 

Main points in pickling . . . . . . . . .122 

Absorbing plant for escaping acid vapors . . . . . .123 

Regaining of acid and metal from exhausted dipping baths ; Mixture 
for the production of a grained surface by pickling . . .124 

Removal of grease ; Preparation of lime mixture ; Cleansing with ben- 
zine . . . . . . . . . . . .125 

Tying the objects to metallic wires ; Removal of oxide from the me- 
tallic objects . . — i . . . . . . . .126 



CHAPTER VI. 

PROCESSES OP ELECTRO-DEPOSITION. 

Importance of the constitution of the water used as a solvent ; Spring 
and well water ; River water ; Distilled water ; Rain water ; Im- 
portance of the purity of the chemicals used . . . . .127 

Examples of the importance of the purity of the chemicals used ; Con- 
centration of the baths . . . . . . . . .128 

Effect of baths too poor in metal and too concentrated ; Stirring up the 
baths 129 

Constant agitation of the baths . . . . . . . .130 

Temperature of the baths ; Boiling of the baths ; Working the bath 
with the electric current ; Dissolution of nickel salts dissolving with 
difficulty 131 

Filtration of the boiled solutions ; Securing lasting qualities to the 
baths; Choice of anodes . . . . . . . .132 

Alloying of the deposit with the basis-metal ; Conditions for an elec- 
trolytic bath 133 

Reduction of metals without a battery (electro-deposition by contact) 133 



XIV CONTENTS. 



CHAPTER VII. 

DEPOSITION OF NICKEL AND COBALT. 
1. Nickeling. 

PAGE 

Growth and popularity of nickel plating ; Properties of nickel . . 135 
Nickel baths ; General rules for preparing nickel baths ; Prepared 
nickeling salts ; Conducting salts . . . . . . . 136 

Additions to nickel baths recommended by various experts ; Boric acid 
as an addition to nickel baths, and its effect . . . . .137 

Determination of the acidity, alkalinity and neutrality of nickel baths ; 
Formulas, preparation, characteristic properties and treatment of 

nickel baths 139 

Nickel baths containing boric acid; Weston's formula ; Kaselowsky's 
formula ........... 141 

Nickel baths for certain purposes ; Nickel bath for rapid nickeling of 
polished slightly coppered zinc articles . . . . . .142 

Nickel bath for iron, brass, copper, sheet zinc and zinc castings ; Re- 
cent formulas for nickel baths ; English formula for a nickel bath ; 
Bruce' s recommendation of the addition of bisulphide of carbon 143 
Nickel bath without nickel salt ; Nickel anodes . . . .144 

Objections to insoluble anodes ........ 145 

Use of rolled and cast anodes together in one bath . . . . 146 

Reddish tinge of the anodes ; Suspension of the anodes ; The process 
of electro-nickeling . . . . . . . . .147 

Coppering or brassing articles previous to nickeling ; Suspension of the 

objects in the bath ; Suitable current-strength for nickeling . . 148 
Burning or over-nickeling ; Criteria for judging whether nickeling pro- 
gresses with a correct current . . . . . . .149 

Most suitable density for nickeling metallic objects ; Solid nickeling . 150 
Test for sufficiently heavy nickeling ; Arrangement of the anodes ; 
Nickeling of flat objects, round, or half-round surfaces, smooth 
articles, objects with depressions and hollows, and lamp feet of cast 
zinc . . . . . . . . ,. . • .151 

General rules for nickeling and other electro- plating processes; Mode 
of suspending the objects in the bath ; Polarizing phenomena ; 
Counter or polarizing current . . . . . . .152 

Nickeling en masse of small and cheap objects . . . . .153 

Warren's solutions of nickel and of cobalt . . . . .154 

Removal of defective and old nickeling ; Remedy against the yellowish 
tone of nickeling . . . . . . . . . .155 

Principal phenomena which may occur in nickeling and the means of 
avoiding them .......... 156 

Refreshing nickel baths 157 



CONTENTS. XV 

PAGE 

Polishing and cleansing nickel deposits ; Treatment of nickled objects 
which are to be left dead ; Nickeling sheet zinc ; Mystery surround- 
ing the nickeling of sheet zinc . . . . . . .158 

Required conditions for, and the execution of nickeling sheet-zinc ; 

Grinding and polishing the sheets ; Construction of cloth bobs . 159 

Manner of polishing or grinding the sheets . . . . .160 

Self-acting sheet polishing machines ; F. Rauber's sheet grinding and 
polishing machine . . . . . . . . . .161 

Freeing the sheets from grease . . . . . . . .163 

Nickeling the sheets ; Advantage of previous coppering or brassing ; 

Great care required in the treatment of the brass bath . . .164 

Coppering of the sheets ; Current-strength for nickeling zinc sheets . 165 
Proportion of anode surface to that of the zinc surface ; Cause of black 
streaks and stains . . . . . . . . . .166 

Augmentation of the metallic content of the bath ; Polishing the 
nickeled sheets ; Nickeling of tin plate and of copper and brass 

sheets 167 

Nickeling of sheet iron and sheet steel . . . . . . .168 

Nickeling of wire ; Apparatus for nickeling wire . . . .169 

Nickeling wire gauze ; Nickeling of knife blades, sharp surgical in- 
struments, etc. .. . . . . . . . .171 

Nickeling of electrotypes, cliches, etc. ; Hard nickeling . . .172 

Formulae for baths for hard nickeling ; Process of hard nickeling ; 

Treatment of the nickeled plates .173 

Recovery of nickel from old baths; Urquhart's plan for recovering 
nickel from old solutions . . . . . . . . 1 74 

To improve defective nickeling ; Arrangement of the " doctor ;" Nick- 
eling by contact and boiling ; Franz Stolba's process of nickeling by 

contact 175 

Deposition of an alloy containing nickel, according to R. Kaiser ; De- 
posits of nickel alloys, and baths suitable for the purpose ; Nickel 
bronze . . . . . . . . . . .177 

French process for the deposition of German silver ; Watt's method . 1 78 

2. Cobalting. 

Properties of cobalt ; Baths for cobalting ; Cobalting of copper plates 
for printing ; Removal of the cobalt coating . . . . .179 

Experiment in stripping the cobalt deposit from cobalted copper plates 
Warren's cobalt solution ; Cobalt solution recommended by Mr. G 
W. Beardslee, of Brooklyn, N. Y 180 

Cobalting by contact 181 



XVI CONTENTS. 

CHAPTER VIII. 

DEPOSITION OF COPPER, BRASS AND BRONZE. 
1 . Coppering. 

PAGE 

Properties of copper 181 

Copper baths, their composition, preparation, properties, and treat- 
ment; Hassauer's copper bath; Copper baths for iron and steel 

articles 182 

Formation of slime on the anodes in a copper bath . . . .183 

Phenomena appearing in copper baths containing cyanide ; Baths for 
coppering zinc articles, recommended by Roseleur . . . . 1 84 

Copper baths without potassium cyanide . . . . . .185 

Weil's copper baths and methods of coppering ; Copper bath recom- 
mended by Walenn ; Gauduin's copper bath ..... 186 

Execution of coppering ; Anodes used ; Scratch-brushing and treat- 
ment of defective places ; Solid and heavy coppering . . .187 
Prevention of the formation of small dark round stains; O. Schulz's 
patent to prevent the formation of stains ; Polishing the deposit of 
copper ............ 188 

Treatment of coppered objects to be coated with another metal; Cop- 
pering small articles en masse ; Coppering by contact and dipping . 189 
Bacco's copper bath ; Brush-coppering . . . . . .190 

Coppering steel pens, needles, eyes, etc. ; Inlaying of depressions of 
copper art-castings with black 191 

2. Brassing {Cuivre poll Deposit). 

Constitution and varieties of brass . . . . . . .191 

Brass baths, their composition, preparation, properties, and treatment ; 
Rule for all baths containing more than one metal in solution ; Brass 
bath according to Roseleur . . . . . . . .192 

Irregular working of fresh brass baths ; Effect of the addition of arse- 
nious acid to brass baths . . . . . . . .193 

On what the color of the brass deposit depends . . . . . 1 94 

Anodes for brass baths ; Formation of slime on the anodes ; Remedy 

against defective deposition . . 195 

Bath for brassing zinc exclusively . 196 

Bath for brassing cast-iron, wrought-iron, and steel ; Norris and John- 
son's brass bath; Solution for transferring any copper-zinc alloy 
serving as anode ; Execution of brassing ; Distance of the objects to 
be brassed from the anodes . . . . . . . .197 

Brassing of unground iron castings ; Brassing by contact and dipping ; 
Inlaying with black of brassed articles . . . . . .198 



CONTENTS. XV11 

3. Bronzing. 

PAGE 

Gountier's solution for coating wrought- and cast-iron with bronze . 198 
Other bronze baths and their composition, preparation, and treatment ; 
Anodes used . . . . . . . . . . .199 

Baths for deposits of tombac ; Execution of bronzing . . . 200 

CHAPTER IX. 

DEPOSITION OF SILVER. 

Properties of silver; Silver baths, their composition, preparation and 
treatment ; Silver bath for a heavy electro-deposit of silver (silvering 
by weight) 200 

Preparation of the bath with silver chloride and of the bath with silver 
cyanide ............ 201 

Silver bath for ordinary electro-silvering ; Vats for silver baths ; Treat- 
ment of the silver baths ; Anodes ....... 202 

Most suitable current-strength for silver baths ; Coupling of the ele- 
ments . . . .203 

Objections to insoluble anodes ; The behavior and appearance of the 
anodes as a criterion of the content of potassium cyanide in the bath ; 
Remedy against two large a content of potassium cyanide ; Keeping 
the bath constant .......... 204 

Proper treatment of baths made with chloride of silver ; Gradual thick- 
ening of the bath .......... 205. 

Method of determining whether the bath contains silver and excess of 
potassium cyanide in proper proportions ...... 206 

Determination of the actual content of silver in the bath ; Contrivances 
for keeping the objects to be silvered in gentle motion while in the 
bath 207 

Singular phenomenon in silvering ; Remedy against a yellow tone of 
silvering 208 

Execution of silvering ; Silvering by weight ; Mechanical and chemical 
preparation of the objects ; Treatment of copper and its alloys \ Ger- 
man silver and brass ; Freeing from grease ; Pickling ; Rubbing . 209 

Pickling in the preliminary pickle ; Amalgamating (quicking) ;. Sling- 
ing wires ; Treatment of the objects while being silvered . 210- 

Amount of silver deposited upon the several grades of plated table ware 
manufactured by the William Rogers Manufacturing Co., of Hartford, 
Conn. ; Method of controlling the weight of the deposit . . .211 

Roseleur's plating balance . . . . . . . . .212.' 

Treatment of objects which are to retain the crystalline dead white with 
which they come from the bath ; Polishing the silvered articles ; Mode 
of executing the operation of burnishing ; Burnishing machines . 215. 
B 



XV111 CONTENTS. 

PAGE 

Ordinary silvering; Practice of the Meriden Britannia Co.'s works of 
Meriden, Conn. ; With Britannia or white metal .... 21(i 

German silver or nickel articles ; Steel articles ; Methods in use in the 
William Rogers Manufacturing Co., Hartford, Conn., for preparing 
work for plating ; For cleansing steel cutlery ; Nickel-silver (German 
silver) for spoons ; Britannia ware (hollow ware) . . . .217 

Rogers' striking solution ; Meriden Company's striking solution ; Extra 
heavy coating of silver on the convex surfaces of spoons and forks ; 
Stopping off; Stopping off varnish . . . . . . .218 

Varnish that will resist the solvent power of the hot alkaline gilding; 
Silvering by contact, by immersion, and cold silvering with paste ; 
Bath for silvering by contact ; Baths for silvering by immersion . 219 

Preparation of solution of sodium sulphide ...... 220 

Dr. Ebermayer's bath for immersion ; Process of coating hooks and 
eyes, pins, etc., with a thin film of silver ..... 222 

Cold silvering with paste ; Composition of argentiferous pastes ; Grain- 
ing 228 

Preparations used for graining ; Mode of obtaining silver powder . 224 

Execution of graining ; Resist and its composition .... 225 

Silvering of fine copper wire ; Incrustations with silver, gold, and other 
metals ............ 22G 

Niel or nielled silvering . . . . . . . . .227 

Imitation of niel by electro-deposition; Old (antique) silvering; Oxi- 
dized silver ........... 228 

Yellow color on silvered articles ; Dissolving silver from silvered art- 
icles (stripping) . . . . . . . . . . 229 

Determination of electro-deposited silvering; Process for the determi- 
nation of genuine silvering used by custom-house officers in Germany ; 
Recovery of silver from old silver baths, etc. ..... 230 

Wet method for the recovery of silver from old silver baths . .231 

CHAPTER X. 

DEPOSITION OF GOLD. 

Properties of gold ; Gold baths, their composition, preparation, and 
properties ........... 232 

Baths for cold gilding .233 

Bath prepared with yellow prussiate of potash ; Gold baths for hot 

gilding 234 

Preparation of the gold baths with the assistance of the electric-current 235 
Management of gold baths ; Anodes ; Employment of anodes of plati- 
num strips or platinum wire for coloring the deposit . . . 23 (> 
Vats for gold baths ; Heating gold baths . . . . .237 



CONTENTS. XIX 

PAGE 

Execution of gilding ; Gilding without a battery and apparatus used 
for the purpose ; Preparation of the articles for gilding . . . 238 

Current-strength for gilding ; Gilding of hollow- ware . . . 239 

Gilding in the cold bath ; Gilding in the hot bath .... 240 

Red gilding; Determination of the content of copper required for ob- 
taining a beautiful red gold ; Green gilding ..... 241 

Rose color gilding ; Method of gilding which is a combination of fire- 
gilding with electro-deposition ; Dead gilding .... 242 

Methods for deadening the surface ; Deadening zinc objects ; Coloring 
of the gilding 243 

Formulae for gilding wax for reddish and greenish gilding ; Preparation 
of gilder's wax ; Application of gilder's wax ; To give gilded articles 
a beautiful rich appearance ; French receipt for the same object . 244 

Improvement of bad tones of gilding ; Incrustations with gold ; Gilding 
of metallic wire and gauze, and J. W. Spaeth's machine for the pur- 
pose ............ 245 

Gold bath for gilding metallic wire and gauze ; Gilding by contact, by 
immersion, and by friction ; Formulae for baths for gilding by dip- 
ping ............ 247 

Gilding by friction or gilding with the rag, with the thumb, with the 
cork ; Martin and Peyraud's method of gilding by friction . . 248 

Removing gold from gilded articles — ''Stripping" .... 249 

Determination of genuine gilding ; Recovery of gold from gold baths ; 

The wet process .......... 250 

Recovery of gold from acid mixtures . . . . . .251 

CHAPTER XI. 

DEPOSITION OF PLATINUM AND PALLADIUM. 

1. Deposition of platinum. 

Properties of platinum : Platinum baths, their composition, preparation 
and properties . . . . . . . . . .251 

Bottger's platinum bath; Preparation of platoso-ammonium chloride; 
Platinum bath patented by "The Bright Platinum Plating Com- 
pany " of London ; Directions for preparing platinum baths by Dr. 

W. H. Wahl ; Alkaline platinate bath 252 

Preparation of an oxalate solution . . . . . . .253 

Preparation of the phosphate bath ....... 254 

Management of platinum baths ; Execution of platinizing ; Platinizing 
of large objects ; Production of heavy deposits .... 255 

Platinizing by contact ; Recovery of platinum from platinum solutions. 256 

2. Deposition of Palladium. 
Properties of palladium ; Palladium bath according to M. Bertrand . 257 



XX CONTENTS. 

CHAPTER XII. 

DEPOSITION OF TIN, ZINC, LEAD, AND IRON. 

1. Deposition of Tin. 

PAGE 

Properties of tin . 1 . . . . . . . .257 

Moire metallique on tin ; Tin baths, their composition, preparation and 
properties ; Direct tinning of objects of zinc, copper, and brass ; 
Previous coppering or preliminary tinning of articles of iron and 
steel ; Alkaline tin bath 258 

Management of tin baths ; Current-strength required ; Anodes ; Choice 
of the tin salt 259 

Refreshing the bath ; Tinning by contact and boiling ; Solutions for 
tinning by contact ; Formula for tinning by immersion . . . 260 

Zilken's patented solution for tinning by contact in a cold bath; Tin- 
ning solution for iron and steel articles ; Tinning for small brass and 
copper articles ; Bottger's solution ; Eisner's bath .... 261 

Stolba's method of tinning . . . . . . . .262 

2. Deposition of Zinc. 

Properties of zinc ; Zinc baths, their composition, preparation and 
properties ........... 262 

Execution of zincking ; Zincking iron by contact ; To coat brass and 
copper with a bright layer of zinc . . . . . . .264 

Zinc alloys ; Production of an alloy of zinc with tin by the use of the 
battery and a suitable bath for the purpose . . . . .265 

3. Deposition of Lead. 

Properties of lead ; Lead baths, their composition, preparation, and 
properties ; Anodes ......... 265 

Leading by contact ; Nobili's rings (iridescent colors, electrochromy) 266 

4. Deposition of Iron (Steeling). 

Principal use of the electro-deposition of iron . . . . .266 

Steel baths, their composition, preparation, and properties ; Baths for 
the production of electrotypes in iron ; Steel bath recommended by 
Klein 267 

Production of a deep black deposit of iron for decorative purposes ; 

Black nickeling ; Management of iron baths ..... 268 

Execution of steeling ; steeling by contact . . . . .269 



CONTENTS. XXI 

CHAPTER XIII. 

DEPOSITION OF ANTIMONY, ARSENIC, AND ALUMINIUM. 

1. Deposition of Antimony. 

PAGE 

Properties of antimony . . . . . . . . .269 

Antimony baths, their composition, preparation, and properties ; Ex- 
plosive property of the antimony deposit . . . . .270 

2. Deposition of Arsenic. 

Properties of arsenic . . . . . . . . .270 

Arsenic baths, their composition, preparation, and properties ; Deposits 
of antimony and arsenic by contact and immersion . . . .271 

3. Deposition of Aluminium. 

Properties of aluminium ; Aluminium baths, their composition, prepa- 
ration, and properties ; Bertrand's process ; Goze's process . . 272 
Mr. Herman Reinbold's formula 273 

CHAPTER XIV. 

GALVAONPLASTY (REPRODUCTION). 

What is understood by galvanoplasty ; Copper the most suitable metal 
for galvanoplastic processes ; Physical properties of copper deposited 
by electrolysis ; Smee's experiments . . . . . .273 

Von HubPs experiments for the determination of the conditions under 
which deposits with different physical properties are obtained ; 
Classes of processes used in galvanoplasty ..... 274 

1. Galvanoplastic Deposition in the Cell Apparatus. 

The cell apparatus . . . . . . . . . .274 

Simple apparatus for amateurs . . . . . . . .275 

Large apparatus ; French form of cell apparatus ; German form of 
cell apparatus .......... 276 

Copper bath for the cell apparatus ; Table giving the approximate con- 
tent of pure crystallized blue vitriol at different degrees Be. and at 

59° F . . . .277 

Method of removing the excess of acid from the bath . . .278 

2. Galvanoplastic Deposition by the Battery and Dynamo Machine. 

Arrangement for the employment of external sources of current . 278 
Depositions with the battery ; Use of the Daniell element and of Bun- 
sen elements ; Coupling the elements 279 

B* 



XX11 CONTENTS. 

PAGE 

Depositions with dynamo machines ; Best dynamos to use ; Copper 
baths for galvanoplastic depositions with a separate source of cur- 
rent ; Bath for depositing with the dynamo ; Bath for depositing 
with the battery; v. Hubl's observations on the elasticity, strength, 
and hardness of galvanoplastic depositions ..... 280 

Most suitable composition for copper printing plates ; Current densities 
for baths at rest and in gentle motion . . . . . .281 

Disadvantage of the difference in the composition of the upper and 
lower layers of the bath . 282 

Various methods of effecting the motion of the bath ; Anodes used 
and their surface in proportion to that of the cathodes . . .283 

Replacement of the copper withdrawn from the bath ; Determination 
of free acid ; Determination of the content of copper according to 
Haen . 284 

Preparation of moulds (matrices) in plastic material ; Suitable materials 
for this purpose .......... 285 

Moulding in gutta-percha ; The "toggle" press . . . . 286 

Hydraulic press . . . . . . . . . .287 

Moulding in wax (stearine) ; Various mixtures ..... 288 

Preparation of the wax mould ; Black-leading and machines used for 
the purpose ........... 289 

Mr. Silas P. Knight's process of black-leading ..... 290 

Preliminary coating of the black-leaded surface with copper; Gilt and 
silvered black-lead 291 

Wiring the mould ; Method of providing as much metallic surface as 
possible; The " electric-connection gripper" ..... 292 

Suspension of the moulds in the bath ; Requisite for the production of 
a dense, coherent and elastic deposit ; Strength of the sulphuric acid 
for filling the clay cells • . . .293 

Most suitable current-density for the production of a good deposit ; 
Coupling of the elements ; Controlling the current by the resistance 
board 294 

Time required for the production of a sufficiently heavy deposit ; Ac- 
cumulators and their use . . . . . . . .295 

Detaching the deposit from the mould ; Backing the deposit or shell . 296 

Composition for backing metal ; Finishing; The saw-table . .297 

Types of power planing or shaving machines ; Mounting the plates ; 

Book plates 298 

Process of making a copy directly from a metallic surface without the 
interposition of wax or gutta-percha . . . . . . 299 

Electro-etching 300 

Composition for etching-ground ; Heliography ; Heliographic process 
invented by Pretsch, and improved by Scamoni .... 301 



CONTENTS. XX111 

PAGE 

Galvanoplastic reproduction of busts, vases, etc. ; Materials for the 
moulds 302 

Moulding undercut reliefs and especially round plastic objects in plaster 
of Paris 303 

Moulding round articles in gutta-percha ; Metallic alloys for the prepa- 
ration of moulds ; Moulding with metallic alloys .... 304 

Taking casts from metallic coins and medals in plaster of Paris ; Casts 
from large plastic objects with undercut surfaces and reliefs in plaster 
of Paris 305 

Making plaster- of- Paris moulds impervious to water .... 306 

Making the moulds conductive ; Metallization by the wet way . .307 

Parkes' and various other methods of metallization by the wet way . 308 

Metallization by metallic powders; Lenoir's process — Galvanoplastic 
methods for originals in high relief . . . . . . .309 

Gelatine moulds and their preparation; Brandley's directions for pre- 
paring gelatine moulds . . . . . . . . .310 

Special uses of galvanoplasty ; Nature printing; Philipp's process for 
coating laces and tissues with copper and then silvering or gilding . 311 

Corvin's niello; Coating grass, leaves, flowers, etc., with copper; 
Plates for the production of imitations of leather . . . .312 

To coat wood, etc., with a galvanoplastic deposit of copper; To protect 
wooden handles of surgical instruments, etc., from the attack of the 
acid copper bath ; Copper deposit for surrounding the mercury ves- 
sels of thermometers ; Metallization of glass, porcelain, clay, terra- 
cotta, etc. ; Galvanoplastic operations in iron . . . . .313 

Conditions for obtaining an anyway successful iron electrotype ; Gal- 
vanoplastic operations in nickel . ... . . . . 314 

Procedure for obtaining a deposit of nickel ; Galvanoplastic operations 
in silver and gold .......... 315 

Bath for galvanoplastic operations with silver ; Bath for galvanoplastic 
operations with gold . . . . . . . . .316 

CHAPTER XT. 

COLORING, PATINIZING, OXIDIZING, ETC., OF METALS. — LACQUERING. 

What is understood by patina and patinizing . . . . .316 

Coloring of copper ; Shades from the pale-red of copper to a dark 

chestnut brown ; Brown color upon copper ; Method used in the Paris 

Mint 317 

Bed-brown color on copper ; To color copper blue-black ; Production 

of cuivre fum6 ; Black color upon copper ; Dead-black on copper ; 

Imitation of genuine patina . . . . . . . .318 

Steel-gray color upon copper ; Dark steel-gray upon copper ; Various 

colors upon massive copper, brass and nickel . . . . .319 



XXIV CONTENTS. 



Coloring of brasses and bronzes ; Lustrous black on brass ; Steel-gray 
on brass ........... 320 

Gray-color with a bluish tint upon brass ; Straw color to brown through 
golden yellow and tombac color on brass ; Color resembling gold on 
brass ; Brown color, called bronze Barb6dienne, on brass . . 321 

Coloring bronze articles dead-yellow or clay-yellow ; Violet and corn- 
flower blue upon brass ; Lustrous colors upon brass .... 322 

Bbermayer's experiments in coloring brass ..... 323 

Coloring zinc; Experiments in coloring zinc black; Puscher's method; 
Neumann's process; Blue-black on zinc; Gray coating on zinc; 
Bronzing on zinc .......... 324 

Red-brown color on zinc ; Yellow-brown shades on zinc ; Coloring of 
iron; Lustrous black on iron ; Meriten's process; Durable blue on 
iron and steel ; Brown-black coating with bronze lustre on iron . 325 

To give iron a silvery appearance with high lustre ; Coloring of tin ; 
Bronze-like patina on tin ; Durable and very warm sepia-brown tone 
upon tin and its alloys ; Dark coloration on tin ; Coloring of silver ; 
Lacquering ........... 326 

Application of lacquer ; Zapon, a new dipping lacquer manufactured 
by the Frederick Crane Chemical Co., Short Hills, N. J. . .327 

Operations of gold varnishers ; Varnishes at the disposal of gold var- 
nishers .328 

Resinous substances and tinctoral matters used in the manufacture of 
varnish ; Removal of varnish from imperfectly varnished objects . 329 

CHAPTER XVI. 

APPARATUS AND INSTRUMENTS. 

Batteries and dynamo machines ; American types of batteries and 

dynamo machines for electro-plating purposes .... 329 

Improved Bunsen cell . . . . . . . . . 330 

The new dynamo-electric machine manufactured by the Hanson & Van 

Winkle Co. of Newark, New Jersey 331 

The "American Giant" dynamo machine manufactured by the Zucker 

& Levett Chemical Company of New York ..... 332 

Vats 333 

Slinging wires ; Conducting wires ....... 334 

Binding posts and rod connections . . . . . . .336 

Lathe for polishing silver plate and silver ; Scratch-brushes ; Dipping 

baskets; Brushes . . . . . . . . . .337 

Kettles and boiling pans ; Stirring rods 33 9 

Glass balloons and flasks ; Evaporating dishes or capsules ; Glass jars ; 

Crucibles . 340 



CONTENTS. XXV 

FAGE 

Hydrometers . 341 

Table showing readings of different hydrometers ; Filters . . . 342 
Siphons 344 

CHAPTER XVII. 

HYGIENIC RULES FOR THE WORKSHOP. 

Neutralization of the action of acids upon the enamel of the teeth and 
the mucous membranes of the mouth and throat ; Protection against 
the corrosive effect of lime and caustic lyes ; Vessels used in the 
establishment not to be used for drinking purposes .... 345 

Precautions in handling potassium cyanide and its solutions ; Sensi- 
tiveness of many persons to nickel solutions ; Poisoning by hydro- 
cyanic (prussic) acid or cyanides ; Remedies to be applied . . 346 

Poisoning by copper salts, by lead salts, by arsenic, by alkalies, by 
mercury salts, by sulphuretted hydrogen, by chlorine, sulphurous 
acid, nitrous and hyponitric gases, and the remedies to be applied . 34 7 

CHAPTER XVIII. 

CHEMICAL PRODUCTS USED IN THE ELECTRO-PLATING ART. 

I. Acids. 

Sulphuric acid and its recognition . . . . . . . 348 

Nitric acid (aqua fortis, spirit of nitre) and its recognition ; Hydro- 
chloric (muriatic) acid and its recognition ; Hydrocyanic acid (prus- 
sic acid) and its recognition . . . . . . . .349 

Citric acid and its recognition ; Boric acid (boracic acid) and its recog- 
nition ; Arsenious acid (white arsenic, arsenic, ratsbane) and its re- 
cognition ........... 350 

Chromic acid and its recognition . . . . . . .351 

II. Alkalies and Alkaline Earths. 

Potassium hydrate (caustic potash) ....... 351 

Sodium hydrate (caustic soda) ; Ammonium hydrate (ammonia or spirits 
of hartshorn) and its recognition ; Calcium hydrate (burnt or quick 
lime) 352 

HI. Sulphur Combinations. 

Sulphuretted hydrogen (sulphydric acid, hydrosulphuric acid) and its 
recognition ........... 352 



XXVI CONTENTS. 

PAGE 

Potassium sulphide (liver of sulphur) and its recognition ; Ammonium 
sulphide (sulphydrate or hydrosulphate of ammonia) ; Carbon di- 
sulphide or bisulphide ; Antimony sulphide ; Black sulphide of anti- 
mony (stibium sulfur atum nigrum) ...... 353 

Red sulphide of antimony (stibium sulfur atum aurantiacum) ; Arsenic 
trisulphide or arsenious sulphide (orpiment) ; Ferric sulphide . . 354 

IV. Chlorine Combinations. 

Sodium chloride (common salt, rock salt) and its recognition ; Ammo- 
nium chloride (sal ammoniac) and its recognition .... 354 

Antimony trichloride (butter of antimony) ; Arsenious chloride ; Copper 
chloride ; Tin chlorides ; Stannous chloride or tin salt and its recog- 
nition ; Stannic chloride ; Zinc chloride (hydrochlorate or muriate 
of zinc, butter of zinc) and its recognition ..... 355 

Zinc chloride and ammonium chloride ; Nickel chloride and its recog- 
nition ; Cobalt chloride and its recognition ; Silver chloride (horn 
silver) and its recognition ........ 356 

Gold chloride (terchloride of gold, muriate of gold, auric chloride) and 
its recognition ; Platinic chloride and its recognition . . .357 

V. Cyanides. 

Potassium cyanide (white prussiate of potash) and its recognition . 358 

Comparative table of potassium cyanides with different content ; Cop- 
per cyanides and their recognition ; Zinc cyanide (hydrocyanate of 
zinc, prussiate of zinc) and its recognition ..... 359 
Silver cyanide (prussiate, or hydrocyanate of silver) ; Potassium ferro- 
cyanide (yellow prussiate of potash) and its recognition . . . 360 

VI. Carbonates. 

Potassium carbonate (potash) and its recognition . . . .360 

Acid potassium carbonate or monopotassic carbonate, commonly called 
bicarbonate of potash ; Sodium carbonate (washing soda) ; Sodium 
bicarbonate (baking powder) ; Calcium carbonate (marble, chalk) ; 

Whiting 361 

Copper carbonate and its recognition ; Zinc carbonate and its recogni- 
tion; Nickel carbonate and its recognition ; Cobalt carbonate . . 362 

VII. Sulphates and Sulphites. 

Sodium sulphate (Glauber's salt) ; Ammonium sulphate and its recog- 
nition 362 

Aluminium potassium sulphate (potash-alum) and its recognition ; 
Ammonium-alum and its recognition ; Iron sulphate (iron protosul- 
phate, ferrous sulphate or green vitriol) and its recognition . . 363 



CONTENTS. XXV11 



Iron- ammonium sulphate ; Copper sulphate (cupric sulphate or blue 
vitriol) and its recognition ; Zinc sulphate (white vitriol) and its 
recognition ; Nickel sulphate and its recognition .... 364 

Nickel ammonium sulphate; Cobalt sulphate and its recognition; 
Cobalt-ammonium sulphate ; Sodium sulphite and bisulphite ; Sodium 
sulphite and its recognition ........ 365 

Sodium bisulphite .......... 366 

VIII. Nitrates. 

Potassium nitrate (saltpetre, nitre) and its recognition ; Sodium nitrate 
(cubic nitre or Chile saltpetre) ; Mercurous nitrate .... 366 

Mercuric nitrate and its recognition ; Silver nitrate (lunar caustic) and 
its recognition .......... 367 

IX. Phosphates and Pyrophosphates. 

Sodium phosphate and its recognition . . . . . .367 

Sodium pyrophosphate and its recognition ; Ammonium phosphate . 368 

X. Salts of the Organic Acids. 

Potassium bitartrate (cream of tartar) ; Potassium sodium tartrate 
(Roehelle or Seignette salt) and its recognition . . . .368 

Antimony potassium tartrate (tartar emetic) and its recognition ; Cop- 
per acetate (verdigris) ; Lead acetate (sugar of lead) and its recog- 
nition ; Sodium citrate ......... 369 

CHAPTER XIX. 

USEFUL TABLES. 

Table of elements with their symbols, atomic weights, and specific 
gravities . . . . . . . . . . .370 

Table of chemical and electro-chemical equivalents ; Explanation of 
the table 371 

Table showing the value of equal current volumes as expressed in 
amperes per square decimetre, per square foot and per square inch 
of electrode surface ; Application of the table . . . .372 

Table showing the specific electrical resistances of different sulphuric 
acid solutions at various temperatures (Fleeming Jenkin) ; Table 
showing the specific electrical resistances of different copper sulphate 
solutions at various temperatures (Fleeming Jenkin) . . .373 

Table of electro-motive force of elements . . . . . .374 

Table showing the solubility of various substances ; Table showing the 
composition of the most usual alloys and solders . . . .375 



XX Vlll CONTENTS. 

PAGE 

Alloys 376 

Solders; Soft solder ; Hard solder; Silver solder . . . .377 

Gold solder ; Table of the melting points of some metals ; Table of 
high temperatures ; Table of the specific gravity and content of 
solutions of potassium carbonate at 57.2° Fahrenheit according to 
Gerlach 378 

Table showing the specific gravity of sulphuric acid at 59° F. according 
to Kolb 379 

Table of the specific gravity and content of nitric acid according to 
Kolb 380 

Table showing the specific gravity of sal ammoniac solution at 66.2° F. 
according to Schiff'; Table showing the electrical resistance of pure 
copper wire of various diameters . . . . . . .381 

Table showing actual diameters in decimal parts of an inch correspond- 
ing to the numbers of various wire gauges . . . . .382 

Index . , . 383 



ELECTRO-DEPOSITION OF METALS. 



i. 

GENERAL HISTORICAL PART. 



CHAPTER I. 

HISTORICAL REVIEW OF ELECTRO-METALLURGY. 

In reviewing the history of the development of electrolysis, 
i. e., the reduction of a metal or a metallic alloy from the solution 
of its salts by the electric current, the simple reduction which 
takes place by the immersion of one metal in the solution of 
another, may be omitted. This mode of reduction was well 
known to the alchemist Zozimus, who described the reduction of 
copper from its solutions by means of iron, while Paracelsus 
speaks of coating copper and iron with silver by simple immer- 
sion in a solution of silver. 

Before the discovery, in 1789, of the electric contact-current, 
by Luigi Galvani, there was nothing like a scientific reduction of 
metal by electricity; and only in 1799, Alexander Volta, of 
Pavia, succeeded in finding the true causes of Galvani's disco- 
very. Galvani observed while dissecting a frog on a table, 
whereon stood an electric machine, that the limbs suddenly 
became convulsed by one of his pupils touching the crural nerve 
with the dissecting knife at the instant of taking a spark from 
the conductor of the machine. The experiment was repeated 
several times, and it was found to answer in all cases when a 
metallic conductor was connected with the nerve, but not other- 
wise. He observed that muscular contractions were produced by 
forming a connection between two different metals, one of which 
2 



18 ELECTRO-DEPOSITION OF METALS. 

was applied to the nerve and the other to the muscles of the leg. 
Similar phenomena having been found to arise when the leg of 
the frog was connected with the electric machine, it could scarcely 
be doubted that in both cases the muscular contractions were pro- 
duced by the same agent. From a course of experiments, Galvani 
drew the erroneous inference that these muscular contractions 
were caused by a fluid having its seat in the nerves, which 
through the metallic connection flowed over upon the muscles. 
Everywhere, in Germany, England, and France, eminent scien- 
tists hastened to repeat Galvani's experiments, in the hope of 
discovering in the organism a fluid which they considered the 
vital principle, but it was reserved for Volta to throw light upon 
the prevailing darkness. In his repeated experiments, this emi- 
nent philosopher observed that one circumstance had been entirely 
overlooked, namely, that in order to produce strong muscular 
contractions in the frog leg experiment it was absolutely necessary 
for the metallic connection to consist of two diiferent metals 
coming in contact with each other. From this he drew the in- 
ference that the agent producing the muscular contractions was 
not a nerve-fluid, but was developed by the contact of dissimilar 
metals, and identical with the electricity of the electric machine. 

This discovery led to the construction of what is known as the 
pile of Volta or the voltaic pile. The same philosopher found 
that the development of electricity could be increased by building 
up in regular order a pile of pairs of plates of dissimilar metals, 
each pair being separated on either side from the adjacent pairs 
by pieces of moistened card-board or felt. On account of various 
defects of the voltaic pile, Cruikshank soon afterwards devised 
his well known trough battery, which consisted of square plates 
of copper and zinc soldered together, and so arranged and fast- 
ened in parallel order in a wooden box that between each pair of 
plates a sort of trough filled with acidulated water was formed. 

Nicholson and Carlisle, on May 2, 1800, first decomposed water 
into hydrogen and oxygen by electrolysis, and, in 1801, Wollaston 
remarked that if a piece of silver in connection with a more posi- 
tive metal, for instance, zinc, be put into a solution of copper, the 
silver will be coated over with copper, which coating will stand 
the operation of burnishing. 



HISTORICAL REVIEW OF ELECTRO-METALLURGY. 19 

Cruikshank, in 1803, investigated the behavior of solutions of 
nitrate of silver, sulphate of copper, acetate of lead, and several 
other metallic salts, towards the galvanic current, and found that 
the metals were so completely reduced from their solutions by the 
current as to suggest to him the analysis of minerals by means of 
the voltaic current. 

To Brugnatelli we owe the first practical results in electro- 
gilding. In 1805, he gilded two silver medals by connecting 
them by means of copper wire with the negative pole of the pile, 
and allowing them to dip in a solution of fulminating gold in 
potassium cyanide, while a piece of metal was suspended in the 
solution from the positive pole. He also observed that the posi- 
tive plate, if it consisted of an oxidizable metal, was dissolved. 

One of the greatest discoveries connected with the subject, how- 
ever, is that of Sir Humphry Davy, made October 6, 1807, when, 
by the decomposition of the alkalies by means of the electric cur- 
rent, he discovered the metals potassium and sodium. 

Prof. Oersted, of Copenhagen, in 1820, found that the mag- 
netic needle is deflected from its direction by the electric current. 
It was known long before this that powerful electric discharges 
affect the magnetic needle ; it had, for instance, been observed 
that the needle of a ship's compass struck by lightning had lost 
its property of indicating the North Pole, and several physicists, 
among them Franklin, had succeeded in producing the same 
phenomena by heavy discharges of the electrical machine, but 
they were satisfied with the supposition that the electric current 
acted mechanically, like the blow of a hammer. Oersted first 
perceived that electricity must be in a state of motion in order to 
act upon magnetism. This led to the construction of the gal- 
vanoscope or galvanometer, an instrument which indicates whether 
the elements or other source of current furnish a current or not, 
and by which the intensity of the source of current may also to 
a certain degree be recognized. 

Ohm, in 1827, discovered the law named after him, that the 
current-strength is proportional to the electro-motive force, i. e. y the 
electrical tension which sets the current in motion, and inversely 
proportional to the resistance; this law will be more fully dis- 
cussed in the theoretical part. 



20 ELECTRO-DEPOSITION OF METALS. 

Ohm's discovery was succeeded, in 1831, by the important dis- 
covery of electric induction by Faraday. By induction is under- 
stood the production of an electric current in a closed circuit 
which is in the immediate neighborhood of a current-carrying 
wire. Faraday further found that the current induced in the 
neighboring wire is not constant, because, after a few oscillations 
the magnetic needle returned to the position occupied by it before 
a current was passed through the current-carrying wire ; whilst 
when the current was broken the needle deflected in the opposite 
direction. 

In the year following the discovery of Faraday, Pixii, of Paris, 
constructed the first electro-magnetic induction machine. 

Faraday's electrolytic law of the proportionality of the current- 
strength and its chemical action, and that the quantities of the 
various substances which are reduced from their combinations by 
the same current, are proportional to their chemical equivalents, 
was laid down and proved in 1833, and upon this Faraday based 
the measurement of the current-strength by chemical deposition 
as, for instance, that of water, in the voltmeter. 

Of the practical electro-chemical discoveries there remain to 
be mentioned the production of iridescent colors, in 1826, by 
Nobili, and the production of the amalgams of potassium and 
sodium, in 1835, by Bird. 

The actual galvanoplastic process, however, dates from the year 
1838. In the spring of 1838, Prof. Jacoby announced to the 
Academy of Sciences of St. Petersburg, a description of his dis- 
covery of the utility of galvanic electricity as a means of repro- 
ducing objects of metal. Hence Jacoby must be considered the 
father of galvanoplasty in as far as he was the first to utilize and 
give practical form to the discoveries made up to that time. 
Though Jacoby's process was published in the English periodical, 
"The Athenaeum," of May 4, 1839, Mr. T. Spencer, who read a 
paper on the same subject, Sept. 13, 1839, before the Liverpool 
Polytechnic Society, claimed priority of invention, as was also 
done by Mr. C. J. Jordan, who, in May 22, 1839, sent a letter to 
the " London Mechanical Magazine/' which was published on 
June 8, 1839. 

From this time forward the galvanoplastic art made rapid 



HISTORICAL REVIEW OF ELECTRO-METALLURGY. 21 

progress, and by the skill and enterprise of such men as the 
Elkingtons, of Birmingham, and de Ruolz, of Paris, it was 
speedily added to the industrial arts. 

Though copies of a metallic object by means of galvanoplasty 
could now be made, the employment of the process was restricted 
to metallic objects of a form suitable for the purpose, until, in 
1840, Murray succeeded in making non-metallic surfaces conduc- 
tive by the application of graphite (black lead, plumbago), which 
rendered the production of galvanoplastic copies of wood-cuts, 
plaster-of-Paris casts, etc., possible. 

Dr. Montgomery, in 1843, sent to England samples of gutta- 
percha, which was soon found to be a suitable material for the 
production of negatives of the original models to be reproduced 
by galvanoplasty. 

Though it was now understood how to produce heavy deposits 
of copper, those of gold and silver could only be obtained in 
very thin layers. Scheele's observations on the solubility of the 
cyanide combinations of gold and silver in potassium cyanide, led 
Wright, a co-worker of the Elkingtons, to employ, in 1840, such 
solutions for the deposition of gold and silver, and it was found 
that deposits produced from these solutions could be developed to 
any desired thickness. The use of solutions of metallic cyanides 
in potassium cyanide prevails at the present time, and the results 
obtained thereby have not been surpassed. 

From the same year also dates the patent for the deposition of 
nickel from solution of nitrate of nickel, without, however, at- 
tracting any special attention, which may have been chiefly due 
to the fact that the deposition of nickel from its nitrate solution 
is the most imperfect and the least suitable for the practice. 

To Mr. Alfred Smee we owe many discoveries in the deposition 
of antimony, platinum, gold, silver, iron, lead, copper, and zinc. 
In publishing his experiments, in 1841, he originated the very 
appropriate term " electro-metallurgy" for the process of working 
in metals by means of electrolysis. 

Prof. Bcettger, in 1842, pointed out that dense and lustrous 
depositions of nickel could be obtained from its double salt, sul- 
phate of nickel with sulphate of ammonium, as well as from 
ammoniacal solution of sulphate of nickel ; and that such 



22 ELECTRO-DEPOSITION OF METALS. 

deposits, on account of their slight oxidability, great hardness and 
elegant appearance were capable of many applications Bcettger's 
statements also fell into oblivion, and only in later years when 
the execution of nickeling was practically taken up in the United 
States, his labors in this department were remembered in Ger- 
many. To Bcettger we are also indebted for directions for coat- 
ing metals with iron, cobalt, platinum, and various patinas. 

In the same year,, De Ruolz first succeeded in depositing metal- 
lic alloys — for instance, brass — from the solutions of the mixed 
metallic salts. In 1843 the first use of thermo-electricity appears 
to have been made by Moses Poole, who took out a patent for 
the use of a thermo-electric pile instead of a voltaic battery for 
depositing purposes. 

From this time forward innumerable improvements in existing 
processes were made ; and also the first endeavors to apply Fara- 
day's discoveries to practical purposes. 

Since 1854, Christofle & Co. have endeavored to replace their 
batteries by magneto-electrical machines, and used the Holmes 
type, better known as the Alliance Machine, which, however, did 
not prove satisfactory ; and besides, the prices of these machines 
were in comparison with their efficiency exorbitant. The machine 
constructed by Wilde proved objectionable on account of its heat- 
ing while working, and the consequent frequent interruptions in 
the operations. 

In 1860 Dr. Antonie Pacinotti, of Pisa, suggested the use of 
an iron ring wound round with insulated wire, in place of the 
cylinder. This ring, named after its inventor, has, with more or 
less modifications, become typical of many machines of modern 
construction. In the construction of all older machines, steel 
magnets had been used, and their magnetism not being constant, 
the eifect of the machine was consequently also not constant. 
Furthermore, they generated alternately negative and positive 
currents, which, by means of commutators, had to be converted 
into currents of the same direction ; and this, in consequence of 
the vigorous formation of sparks, caused the rapid wearing out of 
the commutators. 

These defects led to the employment of continuous magnetism 
in the iron cores of the electro-magnets, the first machine based 



HISTORICAL EEVIEW OF ELECTRO-METALLURGY. 23 

upon this being introduced in 1866, by Siemens, which, in 1867, 
was succeeded by Wheatstone's. 

However, the first useful machine was introduced in 1871, by 
Zenobe Gramme, who in its construction made use of Pacinotti's 
ring. This machine was, in 1872, succeeded by Hefner- Alteneck's, 
of Berlin. In both machines the poles of the electro-magnet 
exert an inducing action only upon the outer wire wrappings of 
the revolving ring, the other portions being scarcely utilized, 
which increases the resistance and causes a useless production of 
heat. This defect led to the construction of flat-ring machines, 
in which the cylindrical ring is replaced by one of a flat shape, 
and of larger diameter, thus permitting the induction of both flat 
sides. Such a machine was, in 1874, built by Siemens & Halske, 
of Berlin ; and in the same year by S. Schuckert, of Nurenberg. 
In Schuckert's modern machines nearly three-quarters of all the 
wire wrappings are under the inducing influence of both of the 
large pole-shoes of the electro-magnets. 

Of other constructions of dynamo-electrical machines may be 
mentioned, Mather's, Weston's, Elmore's, Fein's, Mohring's, 
Krottlinger's, and Lahmeyer's, the latter especially being at the 
present time much employed in Germany for electro-plating pur- 
poses. 

For the sake of completeness there may be mentioned the in- 
vestigators and practitioners who during the last twenty years 
have contributed much to the improvement of the electro-chemi- 
cal processes and the perfection of galvanoplasty. Besides those 
already named, they are : Elkington, Becquerel, Heeren, Rose- 
leur, Eisner, von Leuchtenberg, Meidinger, Weil, Goode, Christ- 
ofle, Klein, von Kress, Thompson, Adams, Gaiffe, and others. 



24 ELECTRO-DEPOSITION OF METALS. 



II. 

THEORETICAL PART. 



CHAPTEK II. 

magnetism and electricity. 

1. Magnetism. 

For the better understanding of the electrolytic laws it will be 
necessary to commence with the phenomena presented by magnet- 
ism, and to consider them more closely. 

A particular species of iron is remarkable for its property of 
attracting small pieces of iron and causing them to adhere to its 
surface. This iron ore is a combination of ferric oxide with fer- 
rous oxide (Fe 3 4 ), and is called load-stone or magnetic iron ore. 
Its properties were known to the ancients, who called it magnesian 
stone after Magnesia, a city in Thessaly, in the neighborhood of 
which it was found. If a natural loadstone be rubbed over a bar 
of steel its characteristic properties will be communicated to the 
bar, which will then be found to attract iron filings like the load- 
stone itself. The bar of steel thus treated is said to be magnet- 
ized, or to constitute an artificial magnet. The artificial magnets 
thus produced may be straight, in the shape of a horseshoe, or 
annular ; but no matter what their form the attractive force will 
appear to be greatest at two points situated near the extremities 
of the bar, and least of all towards the middle. The points of 
the magnet showing the greatest attractive force are called the 
magnetic poles, whilst the line between them, possessing little or 
no attractive force, is termed the neutral line or neutral zone. In 
a closed magnet the poles are situated on the ends of one and the 
same diameter, while the neutral zones are located on the ends of 
a diameter standing perpendicular to the first. 



MAGNETISM AND ELECTEICITY. 25 

When a magnetized bar or natural magnet is suspended at its 
centre in any convenient manner, so as to be free to move in a 
horizontal plane, it is always found to assume a particular direc- 
tion with regard to the earth, one end pointing nearly north and 
the other nearly south. If the bar be removed from this position 
it will tend to reassume it, and, after a few oscillations, settle at 
rest as before. The direction of the magnetic bar, i, e., that of its 
longitudinal axis, is called the magnetic meridian, while the pole 
pointing towards the north is usually distinguished as the north 
pole of the bar, and that which points southward as the south pole. 

A magnet, either natural or artificial, of symmetrical form, 
suspended in the presence of a second magnet, serves to exhibit 
certain phenomena of attraction and repulsion, which deserve 
particular attention. When a north pole is presented to a south 
pole, or a south pole to a north, attraction ensues between them ; 
the ends of the bar approach each other, and, if permitted, adhere 
with considerable force ; when, on the other hand, a north pole is 
brought near a second north pole, or a south pole near another 
south pole, mutual repulsion is observed, and the ends of the bar 
recede from each other as far as possible. Poles of an opposite 
name attract and poles of a similar name repel each other. 

Magnetism was formerly explained by the invention of two 
fluids, but the theory now universally received is that of Ampere. 
Working from the fact that a circular electrical current constitutes 
a magnet at right angles to its plane, and that electro-magnets are 
practically composed of a series of such circular currents ranged 
in the form of helices, and also from the fact that the force is 
evidently possessed completely by the molecules of permanent 
magnets, he taught that magnetic substances are composed of 
molecules around which currents of electricity are constantly 
flowing ; that magnetism consists in ranging all these currents in 
parallel order, and it has been thoroughly proved by the most 
stringent mathematical analysis that this beautiful idea explains 
all the facts of magnetism. 

If an iron or steel needle be suspended free in the neighborhood 
of a magnet it assumes a determined direction according to its 
greater or smaller distance from the poles or from the neutral 
zone ; however, before the needle assumes this direction it swings 



26 ELECTRO-DEPOSITION OF METALS. 

more quickly and with a shorter stroke or slowly with a longer 
stroke according to the greater or smaller attractive force exerted 
upon it. The space within which the magnetic action of a magnet 
is exercised is called the magnetic field, and the magnetic as well 
as the electric attractions and repulsions are, according to Coulomb, 
as the densities of the fluids acting upon each other and inversely 
as the square of their distance. 

2. Electricity. 

In an ordinary state solid bodies exhibit no attractive effect 
upon small light particles, such as strips of paper, balls of elder- 
pith, etc. ; but by rubbing many solid bodies with a piece of dry 
cloth or fur they acquire the property of attracting such light 
bodies as mentioned above. The cause of this phenomenon is 
called electricity, and the bodies which possess this property of 
becoming electric by friction, are termed idioelectrics and those 
which do not appear to possess it, non-electrics. Gray, in 1727, 
found that all non-electric bodies conduct electricity, and hence 
are conductors, while those which become electric by friction are 
non-conductors of electricity. Strictly speaking, there are no non- 
conductors, because the resins, silk, glass, etc., conduct electricity, 
though only very slightly. It is therefore better to distinguish 
good and bad conductors. To test whether a body belongs to the 
idioelectrics, the so-called electroscope is used, which in its simplest 
form consists of a glass rod mounted on a stand, and bent at the top 
into a hook, from which hangs by a silken thread or hair a pith 
ball. If on bringing the rubbed body near the pith ball, the latter 
is attracted, the body is electric, whilst if the ball is not attracted, 
the body is either non-electric or its electricity is too slight to pro- 
duce an attractive effect. 

From the following experiments it was found that there exist 
two kinds of electricity : When a rubbed rod of glass or shellac 
is brought near the ball of elder-pith suspended to a silk thread, 
the ball is attracted, touches the rod, adheres for a few moments 
and is then repulsed. This repulsion is due to the fact that the 
ball by coming in contact with the rod becomes itself electric and 
its electricity must first be withdrawn by touching with the hand 



MAGNETISM AND ELECTKICITY. 27 

before it can be again attracted by the rod. By now taking two 
such balls, one of which has been made electric by touching with 
a glass rod which had been rubbed with silk, and the other by 
touching with a shellac rod rubbed with cloth, it will be observed 
that the ball, which is repulsed by the glass rod, is attracted by 
the shellac rod and vice versa. These two kinds of electricity are 
called vitreous or positive, and resinous or negative electricity, and 
it has been found that electricities of a similiar name attract, and 
electricities of an opposite name, repel each other. 

For want of a concrete knowledge of the electric agent which 
produces the electric phenomena, various theories have been ad- 
vanced to explain these phenomena and the action of the electric 
forces. Only two of the best known theories shall here be men- 
tioned. The adherents of Symmer's theory retain the idea, that 
there exist two different electric fluids ; that each of these fluids 
exerts a strongly repulsive action on its own parts, or bodies sep- 
arately charged with itself, but that each fluid has a strong attrac- 
tion for the other, and both a strong attraction for ordinary matter ; 
that in the ordinary condition of matter the two fluids are united 
in equal proportions, being thus neutralized and adherent to 
matter. 

Franklin devised the one-fluid theory. He supposed that there 
was one electric fluid pervading all matter, possessing a strong at- 
traction for matter, but being strongly self-repulsive : Matter in 
its ordinary state has in connection with it so much fluid as satis- 
fies the mutual attractions, but when certain bodies (electrics) are 
rubbed, some absorb part of the electricity from the rubber and 
thus become positively charged with this overplus ; others part with 
their proper electricity to the rubber, and thus remain negatively 
charged. 

According to Coulomb, the electric attractions and repulsions are 
as the densities of the fluids acting upon each other, and inversely as 
the square of the distance. 

However, a current of electricity is created not only by fric- 
tion, but also by the contact of various metals. In the same 
manner as the copper and iron in Galvani's experiments with the 
frog leg, other metals and conductors of electricity also become 
electric by contact, the electric charges being, however, stronger 



28 ELECTRO-DEPOSITION OF METALS* 

or weaker, according to the nature of the metals. If zinc be 
brought in contact with platinum, it becomes more- strongly posi- 
tively electric than when in contact with copper ; whilst, how- 
ever, copper in contact with zinc is negatively electric excited, in 
contact with platinum it becomes positively electric. By now 
arranging the metals in a series, so that each preceding metal be- 
comes positively electric in contact with the succeeding, a series of 
tension is obtained, in which the metals or conductors of elec- 
tricity stand as follows : — 

-f- Zinc, cadmium, tin, iron, lead, copper, nickel, 
Silver, antimony, gold, platinum, carbon — . 

While two metals of the series of tension touching each other 
become electrically excited in such a manner that one becomes 
positively and the other negatively electric, an exchange of the 
opposite electricities takes place by inserting a conducting fluid 
between the metals. Thus, if a plate of zinc and a plate of cop- 
per connected by a metallic wire are immersed in a conducting 
fluid, for instance, dilute sulphuric acid, the electricity of the 
positive zinc passes through the fluid to the negative copper, and 
returns through the wire, the closing arc, to the zinc. However, 
in the same degree with which the electricities equalize them- 
selves, new quantities of them are constantly formed on the 
points of contact of the metals with the conducting fluid ; and, 
hence, the flow of electricity is continuous. This electric current 
generated by the contact of metals and fluids is called the gal- 
vanic current ; or, since it is generated by the intervention of fluid 
conductors, hydroelectric current. A combination of conductors 
which yields such a galvanic current, is called a galvanic element, 
or a galvanic chain. 

It would here be the place to discuss the various galvanic ele- 
ments ; but it is thought better to describe them in a separate 
chapter, and first to explain the laws and the actions of the gal- 
vanic current. 

Electrical potential. — The property of electricity corresponding 
to head or pressure, as applied in speaking of gas or water-power, 
is termed the electrical potential. Two bodies have the same elec- 
trical potential when, connected by a metallic wire, they develop 
no electricity. 



MAGNETISM AND ELECTRICITY. 



29 



Electro-motive force. — If, however, two bodies connected by 
a metallic wire possess unequal electrical potentials, a movement 
of the electricity takes place, and the force which produces this 
movement or current is called the electro-motive force or tension. 
It, therefore, corresponds to the difference of the potentials ; and 
the magnitude of this difference of the potentials is the measure 
for the electro-motive force. 

Resistance. — All conductors oppose a certain amount of resist- 
ance to the forward movement of the electric current. By con- 
necting, for instance, two bodies charged w T ith electricity, and 
possessing a difference of potentials, by a metallic conductor, a 
certain time is required for the compensation of the difference of 
potentials, or, in other words, before the electrical equilibrium is 
established. By now keeping the difference of potentials con- 
stant, the quantity of electricity which passes through the closing 
conductor, the closing arc, depends on the resistance which the 
latter opposes to the passage of the current. 

The resistance of a conductor is proportional to its length and 
inversely to its cross section and its conducting capacity; i. e., the 
longer the conducting arc, the greater the resistance and the greater 
its cross section, the smaller the resistance. Wires of small diam- 
eter will, therefore, oppose greater resistance to the current than 
those w T ith larger diameter, and wires with good conducting 
capacity will produce less resistance than those with poor con- 
ducting capacity. According to Lazere Weiler, the conductivity 
of metals is as follows : — 



Name of metal. 


Mean 

conductivity. 


Alloys, etc. 


Mean 
conductivity. 


Silver .... 


100.0 


Cu 


with 4 per cent. Si, 


75.0 


Copper 


100.0 


Cu 


" 12 " Si, 


54.7 


Gold .... 


80.6 


Cu 


" 9 " P, 


4.9 


Alu minium 


55.1 


Cu 


" 10 " Pb, 


30.0 


Zinc .... 


30.2 


Cu 


" 10 " Al, 


12.6 


Platinum 


16.7 


Cu 


" 10 " As, 


9.1 


Iron .... 


16.4 


Cu 


" 20 " Sn, 


8.4 


Tin ... . 


15.2 


Cu 


" 35 " Zn, 


21.1 


Lead .... 


8.8 


Cu 


" 50 " Ag, 


86.6 


Nickel 


7.9 


Au 


" 50 " Ag, 


16.1 


Antimony . 


4.2 


Sn 


" 12 " Na, 


46.9 



30 ELECTRO-DEPOSITION OF METALS. 

Quantity of current. Ohm's law. — The quantity of electricity 
or, in other words, the current-strength which an element fur- 
nishes at a determined extreme point depends on the strength of 
the electro-motive force which impels the current, as well as on 
the resistance which the conductor opposes to the current. In 
the preceding it has been seen that the electro-motive force cor- 
responds to the difference of the potentials of two conductors 
connected by a metallic wire ; the greater this difference is the 
greater the energy with which the compensation of the electrici- 
ties takes place will be. It has also been explained that the re- 
sistance increases in proportion to the length, and decreases with 
the increase in the cross-section of the conductor. Upon these 
relations Ohm's law is based, and in its completeness it may be 
summed up as follows : The quantity of electricity or the strength 
{intensity) of current is directly proportional to the sum of the 
electro-motive forces of the exciting elements, and is inversely pro- 
portional to the sum of the resistances of its closing circuit; however, 
the resistance of each part of the closing circuit is proportional to 
its length and inversely proportional to its cross-section. Now, if 
8 indicates the strength of current, E, the sum of the electro- 
motive forces, and L the total resistance, then the strength of 
current S is — 

The total resistance L is, however, composed of two different 
resistances, namely, of the so-called essential or internal resistance, 
which expresses the resistance of the substances in the elements 
themselves, and of the non-essential or external resistance of the 
closing arc. If, therefore, the internal resistance is = R, the ex- 
ternal resistance = r, the total resistance will be L = B + r, and 
the formula given above is changed to 

Let us now examine the useful applications to the coupling of 
elements which result from Ohm's laws, and which are of great 
importance to the practical electro-plater. According to the 
above formula, which expresses the total performance of a bat- 



MAGNETISM AND ELECTRICITY. 31 

tery, the strength of current of a single element is, if s indicates 
its current-strength, e the electro-motive force, R the essential in- 
ternal resistance, and r the resistance in the closing arc, 

e 

s = . 

R + r 

By now uniting several such elements, let us say n elements, 
to a column, the electro-motive force of the latter has become 
n + e = n e, and the internal resistance nr; with the same closing 
arc as that of the single element, r will not increase, hence the 
strength of current of these n elements must be written — 

ne 

s = . 

n R + r 

It is now clear that when a determined closing arc of the re- 
sistance r is given that the strength of current cannot be indefi- 
nitely augmented by increasing the number of n elements ; be- 
cause, though the electro-motive force, by the augmentation of n 
elements, increases by so many n, the internal resistance R also 
grows, so that finally the value r, which remains constant, disap- 
pears contrary to the resistance R, which increases n times. 
Hence, the strength of current constantly approaches more the 
limit of value — 

ne e 

^r~r' 

On the other hand, the effect can neither be increased by 
enlarging the area of the pair of plates or by decreasing the re- 
sistance of the fluid in a given number of elements. Because, 
when r, the external resistance, is sufficiently large so that the 
internal resistance, n R, may be neglected, the intensity always 

approaches more the value - . 

r 

Hence, it follows that the augmentation of the area of the ex- 
citing pair of plates produces an increase in the current-strength 
only ivhen the external resistance in the closing arc is small in pro- 
portion to the internal resistance of the battery. 

If we now apply the results of the above explanations to the 
practice we find that the elements may be coupled in various 
ways according to requirement. 



32 



ELECTRO-DEPOSITION OF METALS. 



1. If, for instance, four Bunsen elements (carbon-zinc) are 
coupled one after another in such a manner that the zinc of 
one element is connected with the carbon of the next, and so on 
(Fig. 1), the current passes four times in succession through an 
equally large layer of fluid, in consequence of which the internal 

Fig. l. 

resistance, 4 R, is four times greater than that of a single element, 
while the resistance of the closing arc, r, remains the same. Hence, 
whilst the current-strength is thereby not increased, the electro- 
motive force is, and for this reason this mode of coupling is called 
the union or coupling of the elements for tension. 

Fig. 2. 




Fig. 3. 



2. By connecting four elements alongside of each other, i. e., all 
the zinc plates and all the carbon plates one with another (Fig. 2), 
the current simultaneously passes through the same layer of fluid 

in four places; the internal resistance 
of the battery is therefore the same as 
that of a single element, and since the 
area of the plates is four times larger 
than that of a single element, the 
quantity of current is augmented by 
this mode of coupling. This is called 
coupling for quantity of current. 

3. Two elements may, however, be 

connected for tension, and several such 

groups coupled alongside of each other 

h as shown in Fig. 3, whereby, according 




MAGNETISM AND ELECTRICITY. 33 

to what has been said above, the electro- motive force as well as 
the current-strength is augmented. This mode of connection is 
called mixed coupling. 

According to the resistance of the bath as well as of the exte- 
rior closing arc, and the surfaces to be plated, the electro-plater 
may couple his elements in either way, and in speaking later on 
of the elements the various modes of coupling will be further 
discussed. We will here only mention the proposition deduced 
from Ohm's law that a number of galvanic elements yield the 
maximum of intensity of current when they are so arranged that 
the internal resistance of the battery is equal to the resistance in the 
closing arc. Hence, when operating with baths of good conduc- 
tivity and slight resistance, for instance, acid copper baths, silver 
cyanide baths, etc., with a slight distance between the anodes and 
the objects and with a large anode-surface, it will be advantage- 
ous to couple the elements alongside of each other for quantity; 
however, for baths with greater resistance, and with a greater 
distance of the anodes from the objects, and with a smaller anode 
surface it is best to couple the elements one after the other for tension. 

The effects of the electric current are thermal, physiological, 
electro-magnetic, inductive, and chemical ; however, for our pur- 
poses, only the last three need be discussed. 

Electro-magnetism. 

If a wire conveying the electric current be brought near a 
magnetic needle, the latter will immediately be deflected from its 
direction, no matter whether the wire conveying the current be 
placed alongside, above, or beneath the magnetic needle. The 
direction which the needle will assume when placed in any 
particular position to the conducting wire may be determined by 
the following rule : Let the current be supposed to pass through a 
watch from the face to the bach; the motion of the north pole will 
be in the direction of the hands. Or, let the observer imagine him- 
self swimming in the direction of the current with his face towards 
the needle ; the north pole of the needle will then be deflected towa? % ds 
his left hand. 

When the needle is subjected to the action of two currents in 
3 



34 ELECTRO-DEPOSITION OF METALS. 

opposite directions, the one above and the other below, they will 
obviously concur in their effects. The same thing happens when 
the wire carrying the current is bent upon itself and the needle 
placed between the two portions ; and since every time the bend- 
ing is repeated a fresh portion of the current is made to act in 
the same manner upon the needle, it is easy to see how a current, 
too feeble to produce any effect when a simple straight wire is 
employed, may be made by this contrivance to exhibit a powerful 
action on the magnet. It is on this principle that instruments 
called galvanoscopes, galvanometers, or multipliers are constructed. 
They serve not only to indicate the existence of electrical currents, 
but also to show by the effects upon the needle the direction in 
which they are moving. The delicacy of the instrument has been 
increased by Nobili through the use of a very long coil of wire, and 
by the addition of a second needle. This instrument is known 
as the astatic galvanometer. The two needles are of equal size 
and magnetized as nearly as possible to the same extent ; they 
are then immovably fixed together parallel, and with their poles 
opposed, and hung by a long fibre of untwisted silk, with the 
lower needle in the coil and the upper one above it. The advan- 
tage thus gained is twofold; the system is astatic, unaffected, or 
nearly so, by the magnetism of the earth ; and the needles being 
both acted upon in the same manner by the current, are urged 
with much greater force than one alone would be, all the actions 
of every part of the coil being strictly concurrent. A divided 
circle is placed below the upper needle, by which the angular 
motion can be measured, and the whole is inclosed in glass, to 
shield the needles from the agitation of the air. 

The deflection of the magnetic needle by the electric current 
has led to the construction of instruments which allow of the 
intensity of the current being measured by the magnitude of the 
deflection. Such instruments are, for instance, the tangent gal- 
vanometer, the sine galvanometer, etc., but they are almost exclu- 
sively used for scientific measurements, while for the determina- 
tion of the intensity of current for electro-plating purposes other 
instruments are employed, which will be described later on. 
However, the electric current exerts not only a reflecting action 
on magnetic needles, but is also capable of producing a magnetiz- 



MAGNETISM AND ELECTRICITY. 35 

ing effect on iron and steel. If a bar of iron be surrounded by 
a coil of wire, covered with silk or cotton for the purpose of 
insulation, it becomes magnetic so long as the current is conducted 
through the coil. Such iron bars converted into temporary mag- 
nets by the action of the current are called electro-magnets, and 
they will be the more highly magnetic the greater the number of 
turns of the coil, and the more intense the current passing through 
the turns is. 

However, not only the iron bar, around which the current 
circulates, becomes magnetic, but also a conducting wire through 
which passes a strong current. By suspending a circular con- 
ducting wire so that it is free to move around its vertical axis, its 
direction is affected by the magnetism of the earth and it will 
take up a position so that its plane stands at a right angle to the 
plane of the magnetic meridian ; by now conducting the current 
through a wire having the form of a long helix, a so-called sole- 
noid, the wire will, in a like manner, place itself with the turns 
of the helix at right angles to the plane of the magnetic meridian, 
or, in other words, the axis of the solenoid will lie in the mag- 
netic meridian. 

In the same manner as an electrified conducting wire acts upon 
a magnet, two electrified wires exert an attracting and repelling 
influence on each other, the general law of the action being that, 
electric currents moving in parallel lines attract one another if they 
move in the same direction, and repel one another if they move in 
opposite directions. 

Induction. 

By induction is understood the production of an electric cur- 
rent in a closed circuit which is in the immediate neighborhood 
of a current-carrying wire. 

Suppose we have two insulated copper-wire spirals, A and B 
(Fig. 4), B being of smaller diameter and inserted in A. When 
the two ends of B are connected with the poles of a battery a 
current is formed in A the moment the current of B is closed. 
This current is recorded by the deflection of the magnetic needle 
of a multiplier, M, which is connected with the ends of A, the 



36 



ELECTRO-DEPOSITION OF METALS. 



deflection of the needle showing that the current produced in A 
by the current in B moves in an opposite direction. The current 
in A, however, is not lasting because, after a few oscillations, the 
magnetic needle of the multiplier returns to its previous position 




and remains there no matter how long the current may pass 
through B. If, however, the current in B be interrupted, the 
magnetic needle swings to the opposite direction thus indicating 
the formation of a current in A, which passes through it in the 
same direction as the interrupted current in B. 

The current causing this phenomenon is called the primary or 
inductive current, and that produced by it in the closed circuit the 
secondary or induced current. From what has been above said, 
it is clear that an electric current at the moment of its formation 
induces in a neighboring closed circuit a current of opposite direc- 
tion^ but when interrupted, a current of the same direction. 

In the same manner as closing and opening the inductive 
current, its sudden augmentation also affects the induction of a 
current of opposite direction in a neighboring wire, while its 
sudden weakening induces a current of the same direction ; the 
same effect being also produced by bringing the inductive wire 
closer to, or removing it further from the neighboring wire. The 
induced currents being alternately formed by opening and closing 



MAGNETISM AND ELECTRICITY. 37 

the circuit, and they showing different directions, the term alter- 
note currents has been applied to them. 

If the turns of the spirals are very close together, each turn 
induces the other, the so-called extra currents being thereby formed. 

The induced currents follow Ohm's law the same as the induc- 
tive current. A long inducing wire with a small cross section 
offers greater resistance than a short wire with a larger cross 
section, and consequently in the first case the current will possess 
slighter intensity and higher tension, and in the other greater 
intensity and less tension. 

In the same manner as an electrified wire induces a current in 
a neighboring wire, a magnet or electro- magnet also produces 
induced currents in a coil of wire surrounding it. These currents 
act in the same manner as those produced by other means, and 
by taking into consideration Ohm's law currents of great and 
slight intensity can be" produced at will, as will be seen in speak- 
ing of the dynamo-electric machines, the construction of which is 
based upon the principle of induction. 

Chemical actions of the electrical current — Electrolysis. 

An electric current on being conducted through a fluid effects 
the reduction of its constituents. By cutting, for instance, the 
conductor of an electric current and introducing the two wire 
ends thereby formed into water acidulated with dilute sulphuric 
acid, the water, provided the current is strong enough, is decom- 
posed into its constituents, hydrogen and oxygen, the former 
separating in the form of gas on the negative pole and the latter 
on the positive. If such a decomposition does not take place, 
the fluid does not conduct the current. Pure water by itself is a 
bad conductor, and to make its decomposition possible, it has to 
be made conductive by acidulation with dilute sulphuric acid. 
When a chemical composition is decomposed by the current, the 
constituent forming the basis of the combination separates on the 
negative pole, and that constituting the acid on the positive ; 
hence metals and hydrogen are liberated on the negative, and 
acids and oxygen on the positive pole. To Faraday is due the 
discovery of the chemical actions of the current and the exposi- 



38 ELECTRO-DEPOSITION OF METALS. 

tion of the laws governing the separation of the constituents. 
He adopted the term electrolysis for the galvanic separation of 
chemical combinations; and electrolyte for the fluids subjected to 
galvanic decomposition. To the poles or plates leading the cur- 
rent into and out of the electrolyte he applied the term electrodes, 
the positive pole being the anode, and the negative pole the 
cathode. The elements of the electrolyzed liquid, which are 
liberated by the action of the current are termed ions, those set 
free on the anode or positive electrode being termed anions, and 
those at the cathode or negative anode cations. Thus, when 
acidulated water is electrolyzed, two ions are evolved, namely, 
oxygen and hydrogen, the former at the positive, and the latter 
at the negative electrode. 

It is absolutely necessary for the electrolyte to be in a fluid state, 
though it does not matter whether the fluid state is produced by 
solution or fusion. 

We know no more of the actual cause of the chemical action of 
electricity than of its nature and origin. According to Clausius's 
theory, matter is composed of minute articles called molecules 
which, though mechanically indivisible, are chemically divisible ; 
the constituent parts of the molecules which are no further chem- 
ically divisible are called atoms. Clausius supposes that the mole- 
cules are in constant motion, that in solid bodies they move around 
determined positions of equilibrium, while in fluids even appa- 
rently tranquil, they move from one place to another, constantly 
revolving and pushing against one another without being subjected 
to a return to their original positions. In pushing against one an- 
other the molecules are decomposed into the atoms of which they are 
composed ; those atoms, however, which have become electro-nega- 
tive under the influence of the current endeavor to reach the anode, 
while those which have become electro-positive move towards the 
cathode. But in doing this they meet atoms of opposite polarity 
with which they reunite to a molecule until they are again liber- 
ated by this molecule pushing against another when they move 
further towards the anode. Arriving at the electrodes they find 
no more atoms of opposite polarity with which they might unite 
to a molecule ; both atoms, therefore, remain free on the electrodes 
while the electrolyte between the two electrodes suffers no percep- 



MAGNETISM AND ELECTRICITY. 



39 



tible change. The atoms are, therefore, to be considered as ions. 
However, in order that the ions may be attracted by the electrodes, 
a current of determined electro-motive force is required ; as other- 
wise, though the electrolyte may conduct the current, the atoms 
attract one another more vigorously than they are attracted by the 
electrode and again form molecules. To this mutual attraction of 
the atoms of opposite polarity is due the resistance of the electro- 
lyte to the transmission of the current and also the formation of a 
current of an opposite direction to that of the primary current, 
which is called the counter or polarizing current. • This counter 
current which is so effectually utilized with accumulators (secondary 
batteries) is the worst enemy of the electro-plater, and to over- 
come it very strong currents have frequently to be used as will 
be shown, for instance, in nickeling sheet zinc. 

Faraday is also the discoverer of the following electrolytic laws: 
First law. The quantity of substance separated within a deter- 
mined time by the current is directly proportional to the strength of 
the current. By conducting the cur- 
rent through a voltameter (Fig. 5), 
i e., a closed decomposing cell pro- 
vided with two platinum electrodes, 
which are in contact with the poles 
of the element, and dip into acidu- 
lated water, oxygen evolves on the 
positive electrode, and hydrogen on 
the negative. The gas mixture (oxy- 
hydrogen gas) is conducted through 
a bent tube inserted air-tight in the 
stopper of the cell, into graduated 
tubes, in such a manner that the gas 
enters under water the tubes which 
are also filled with water ; the escap- 
ing mixture of gas rises in the form 
of bubbles into the upper part of 
the tube, and the volume of gas 
there collected in a determined time can be readily read off. 

Now, if a current of determined strength has produced a de- 
termined quantity of oxy hydrogen gas in the voltameter, a cur- 




40 ELECTRO-DEPOSITION OF METALS. 

rent twice as strong will, according to Faraday's law, produce in 
the same time double the volume of gas, from which further re- 
sults the fact that for the decomposition of a determined quantity 
of any body, a constant quantity of current is always required, 
to which the term electrical equivalent might be applied. 

Second law. If the same current acts upon a seines of different 
solutions the weights of the elements separated at the same time in 
each solution are proportional to their chemical equivalents. If, 
for instance, the same current be conducted through three decom- 
posing cells, one of which contains water, the second a solution of 
blue vitriol and the third a solution of nitrate of silver, for each 
gramme of hydrogen developed in the first cell, 31.75 grammes 
of copper will be separated in the second cell and 108 grammes 
of silver in the third cell, because their chemical equivalents are 
as 1:31.75: 108. 

Third law. In an element, the chemical decomposition — the dissolu- 
tion of zinc — is proportional to the strength of current ; or, in other 
words, as many equivalents of zinc are dissolved in the element as 
equivalents of another metal are separated in an inserted electrolyte. 
Every electro-plater observes that the zinc cylinders of the ele- 
ments are dissolved ; and it is just this solution which maintains 
the development of the electric current. As is well known, zinc 
is strongly attacked and dissolved by dilute sulphuric acid ; there- 
fore a dissolution of zinc takes place before the galvanic apparatus 
is closed. This dissolution of zinc independent of the production of 
current is termed local action, and to decrease it the zinc is amal- 
gamated by first washing it with strong soda to remove grease. 
Then it is dipped into a vessel of water containing ypth of sulphuric 
acid ; and as soon as strong action takes place, transferred to a suita- 
ble dish, and mercury poured over it, and it is rubbed well till a 
bright silver-like film forms ; then it is set up on edge to drain, and 
before use any globules set free are rubbed off. If local action 
has thus been prevented, only as much zinc will dissolve, according 
to this law, as is chemically equivalent to the metal separated in 
the decomposing cell. If, however, local action is present, the 
consumption of zinc is increased by the quantity corresponding to 
solution by local action. 

Electro-chemical equivalents. — This term is applied to the 



MAGNETISM AND ELECTRICITY. 41 

weights of the various electrolytes which are decomposed in the 
unit of time by the electric unit. The electro-chemical equiva- 
lents are proportional to their chemical equivalents. The electro- 
chemical equivalent of a body is found by multiplying its chemi- 
cal equivalent by the electro-chemical equivalent of hydrogen 
= 0.0001022. 

When an electric current passes through a conductor, the latter 
becomes more or less heated. According to Joule's experiments, 
it was found that the development of heat in the conductor is pro- 
portional to its resistance; and further, that it is proportional to the 
square of the strength of current. 

Hence the development of heat will be the greater the smaller 
the cross section of the conductor and its conducting capacity 
are ; and the larger the quantity of current which passes through 
it. For practical purposes, the conclusion derived from this is 
the necessity of choosing conducting wire of good conducting 
capacity and of sufficiently large diameter to prevent the develop- 
ment of heat, which, in this case, means loss of current. 

Consumption of power in the electrolysis. — Without a desire fur- 
ther to enter into the details of the electro-chemical theory, it 
may, for the sake of completeness be mentioned that the force re- 
quired for the decomposition of an electrolytic solution is at least 
equal to that which, when converted into heat, corresponds to the 
heat developed by the separated bodies in their reunion into their ori- 
ginal combination. 

Electric units. — The electro-motive force required for the de- 
composition being frequently given, as well as the intensity which 
the current must possess in order to properly coat a determined 
surface of articles with the electrolytically separated metal, the 
electric units serving for electric measures will be briefly given : 

To measure the physical phenomena of the current it is neces- 
sary to refer to mass, length and duration of time, and the units 
adopted by the International Congress of 1881, are as follows : — 

1. Unit of length, 1 centimetre. 

2. Unit of time, 1 second. 

3. Unit of mass, the mass of one gramme. 



42 ELECTRO-DEPOSJTION OF METALS. 

The term fundamental or C. G. S. (centimetre-gramme-second), 
units has been applied to this system. 

Force or power (F) — Dyne. — Force which acting upon 1 
gramme for a second generates a velocity of 1 centimetre per 
second. 

Work. — Erg. — Amount of work done by 1 dyne working 
through 1 centimetre of distance. 

Quantity. — The quantity conveyed by unit current in 1 second. 

Potential or electromotive force. — The difference of the electric 
condition between two conductors or two points of a conductor, 
when the transference of electricity from one to the other is pro- 
ceeding at the rate of 1 erg of work per unit of electricity trans- 
ferred. 

Resistance. — A resistance such that with unit of difference of 
potential between the ends of conductor, 1 unit of current is con- 
veyed along it. 

Of the so-called practical units, which were retained by the 
Congresses and Conferences of 1881 and 1884, there are five : the 
ohm, volt, ampere, farad, and coulomb. 

The ohm is the practical unit of resistance. It is equal to the 
resistance of a column of mercury 1 metre long and 1 square mil- 
limetre in cross-sectional area at 0° C, and approximately equal 
to the resistance of 48.5 metres of pure copper-wire, 1 millimetre 
in diameter at 0° C. The ohm is equal to 10 9 C. G. S. units. 

The ampere is the practical unit of the current-strength (inten- 
sity) ; it is equal to j- 1 ^ of the theoretical C. G. S. unit. For 
practical purposes the quantity of silver precipitated in one second 
is taken as the representative value of an ampere, 0.0011188 
gramme of silver corresponding, according to Kohlrausch, to 
one ampere. 

The volt is the practical unit of the electro-motive force, and is 
equal to 10 8 C. G. S. units. It is approximately equal to the 
electro-motive force of a single DanielPs cell. 

The farad is the practical unit of capacity equal to 10 9 C. G. S. 
units ; the coulomb is the unit of quantity, i. e., the volume of 
current equal to that of 1 ampere passing through a circuit for 
one second of time. 



MAGNETISM AND ELECTRICITY. 43 

A current of 1 ampere at the pressure of 1 volt is termed a 
watt ; it is a most useful unit for comparing different currents, 
and is really the product of volume into pressure. 

The English horse-power (H P) is taken at 550 foot-pounds 
per second, and is thus equivalent to raising 550 pounds through 
one foot; or, one pound through 550 feet in a second. (The 
French H P is 542.48 foot-pounds per second.) 



44 ELECTRO-DEPOSITION OF METALS. 



III. 

SOURCES OF CURRENT. 



CHAPTEK III. 

GALVANIC ELEMENTS — THERMOPILES — MAGNETO- AND 
DYNAMO-ELECTRIC MACHINES. 

The sources of current used for electro-depositions of metals 
are the galvanic elements, thermo-piles, magneto-electric machines, 
and dynamo-electric machines. 

A. Galvanic Elements. 

It is not proposed to enter into a detailed description of all the 
forms of galvanic elements because the number of such construc- 
tions is very large, while the number of those which have been 
successfully and permanently introduced for practical work is 
comparatively small. 

The original form of the galvanic elements, the voltaic pile, 
consisting of zinc and copper plates separated from one another 
by moist pieces of cloth, has been already mentioned on p. 18, as 
well as its disadvantages which led to the construction of the so- 
called trough battery. The separate elements of this battery are 
square plates of copper and zinc, soldered together and parallel, 
fixed into water-tight grooves in the sides of a wooden trough so 
as to constitute water-tight partitions which are filled with acidu- 
lated water. The layer of water serves here as a substitute for 
the moist pieces of cloth in the voltaic pile. 

In other constructions the fluid is in different vessels, each 
vessel containing a zinc and a copper plate which do not touch 
one another in the same vessel, the copper plate of the one vessel 
being connected with the zinc plate of the next, and so on. 



GALVANIC ELEMENTS, THEKMO-PILES, ETC. 45 

In all elements with one fluid as an excitant, the current is 
quite strong at first but quickly decreases for the following rea- 
sons : First, during the interruption of the current a change takes 
place in the fluid by the local action in the element, and then 
with a closed circuit the zinc with the impurities it contains forms 
small voltaic piles, the element consequently also performing a 
certain chemical work during the interruption of the current. As 
mentioned on p. 40, the local action can be reduced to a minimum 
by amalgamating the zinc. Such amalgamation is also a protec- 
tion against the above-mentioned chemical work of the element, 
the bubbles of hydrogen adhering so firmly to the amalgamated 
homogeneous surface as to form a layer of gas around the zinc 
surface, which prevents its contact with the fluid. 

Amalgamation may be effected in various ways. The zinc is 
either scoured with coarse sand moistened with dilute sulphuric 
or hydrochloric -acid, or pickled in a vessel containing either of 
the dilute acids. The mercury may be either mixed with moist 
sand and a few drops of dilute sulphuric acid, and the zinc be 
amalgamated by applying the mixture by means of a wisp of 
straw or a piece of cloth ; or the mercury may be applied by itself 
by means of a steel wire brush, the brush being dipped in the 
mercury, and what adheres quickly divided upon the zinc by 
brushing until the entire surface acquires a mirror-like appear- 
ance. The most convenient mode of amalgamation is to dip the 
zinc in a suitable solution of a mercury salt and rub with a woolen 
rag. A suitable solution is prepared by dissolving 10 parts by 
weight of mercurious nitrate in 100 parts of warm water, to which 
pure nitric acid is added until the milky turbidity disappears. 
Another solution, which is also highly recommended, is obtained 
by dissolving 10 parts by weight of mercuric chloride (corrosive 
sublimate) in 12 parts of hydrochloric acid and 100 of water. In 
order to preserve as much as possible the coating of mercury of 
the zinc, sulphuric acid saturated with neutral mercuric sulphate 
is used for the elements ; for which purpose frequently shake the 
concentrated sulphuric acid (before diluting with water) with the 
mercury salt. 

Bouant recommends instead of the addition of mercuric sulphate, 
to compound the dilute sulphuric acid with 2 per cent, of a solu- 



46 ELECTRO-DEPOSITION OF METALS. 

tion obtained as follows : Boil a solution of 3 J ozs. of nitrate of 
mercury in 1 quart of water, with an excess of a mixture of equal 
parts of mercuric sulphate and mercuric chloride, and, after cool- 
ing, filter and use the clear solution. 

The third reason for the decrease of the current-strength in 
elements with one fluid is polarization. By polarization is under- 
stood the appearance in the element of a second current which, 
being opposite to that produced by the element, weakens the action 
of the latter. The cause of galvanic polarization is found in the 
fact that the negative pole-plate becomes coated with a layer of 
hydrogen, whereby according to Clausius's theory (p. 38) the 
attraction of the anodes for the ions is essentially weakened, while, 
according to another theory, the electro-negative plate, by con- 
tact with the layer of gas, becomes electro-positive towards the 
other which is coated with bubbles of oxygen. 

Polarization can only be entirely avoided in elements the nega- 
tive pole-plate of which dips into a fluid which oxidizes the 
hydrogen to water, as is the case in the so-called constant elements 
with two fluids, as will be seen later on. 

Proceeding from the conviction that rough surfaces allow the 
bubbles of hydrogen to pass off much more freely than smooth 
surfaces, Smee constructed the element named after him. It 
consists of a zinc plate and a platinized silver plate dipping into 
dilute acid. It may be formed of two zinc plates mounted with 
the platinized silver between them in a wooden frame, which being 
a very feeble conductor may carry away a minute fraction of the 
current, but serves to hold the metals in position so that quite a 
thin sheet of silver may be employed without fear of its bending 
out of shape and making a short circuit. The platinizing is 
effected by hanging the silver plates in a vessel filled with acidu- 
lated water, adding some chloride of platinum and placing the 
vessel in a porous clay cell filled with acidulated water and con- 
taining a piece of zinc, the latter being connected with the silver 
plates by copper wire. The platinizing obtained in this manner 
is a black powder which roughens the surfaces in consequence of 
which the bubbles of hydrogen become readily detached and the 
polarization is less than with silver plates not platinized. The 
use of electrolytically prepared copper plates, which are first 



GALVANIC ELEMENTS, THERMO-PILES, ETC. 



47 



Fig. 6. 



strongly silvered and then platinized, is still more advantageous 
on account of their greater roughness. To increase the constancy 
of the element it is advisable to add some chloride of platinum 
to the dilute acid of the element. The electro-motive force of the 
Smee element is about 0.48 volt. 

As previously mentioned polarization can be entirely avoided 
only by allowing the electro-negative pole plate to dip in a fluid 
which, by combustion, reduces the hydrogen evolved to water, 
or in other words, which immediately oxidizes the hydrogen to 
water. From this conviction originated the so-called constant 
elements with two fluids, the first of these elements being, in 1829, 
constructed by Becquerel, which, in 1836, was succeeded by the 
far more effective one of Daniell. 

As most generally used Daniell's element (Fig. 6) consists of a 
glass vessel, a copper cylinder, a porous clay cell, and a rod of 
zinc suspended in the latter. The glass ves- 
sel is filled with concentrated solution and 
a small piece of blue vitriol, and the porous 
clay cell with dilute sulphuric acid. The 
oxygen evolved on the electro-positive zinc 
oxidizes the laiter, sulphate of zinc being 
formed, while the hydrogen separating on 
the electro-negative copper reduces from the 
blue vitriol solution a quantity of copper 
equivalent to it, which separates upon the 
electro-negative plate. However, after a 
comparatively short time of working, the 
dilute sulphuric acid is consumed for the formation of sulphate 
of zinc, the electro-motive force becoming very weak, and the 
necessity of frequently renewing the dilute sulphuric acid is an 
inconvenience which the Daniell elements show more than any 
others. Furthermore, by the action of osmose blue vitriol solu- 
tion gets into the porous cell, where it is decomposed by coming 
in contact with the zinc, the copper being separated upon the 
latter, whereby the effect is destroyed or at least very much 
weakened. The electro-motive force of the Daniell element is 
about 1 volt. 




48 



ELECTRO-DEPOSITION OF PETALS. 



Fig. 7. 



The Meidinger element may be considered a modified Daniell 
element. Like the Callaud element it has no porous division, 
the mixture of the two fluids being prevented by their different 
specific gravities. The shape of the Meidinger element, as most 
generally used, is shown in Fig. 7. 

Upon the bottom of a glass vessel, A, provided at b with a 
shoulder, stands a small glass cylinder, K, which contains the 
electro-negative copper cylinder D; from 
the latter a conducting wire leads to the 
exterior. Upon the shoulder at b rests the 
zinc cylinder Z, which is also provided with 
a conducting wire leading to the exterior. 
The balloon C closes the vessel by being 
placed upon it. The balloon is filled with 
pieces of blue vitriol and Epsom salt solu- 
tion ; the entire element is also filled with 
Epsom salt solution (1 part Epsom salt to 
5 water). In the balloon C concentrated 
solution of blue vitriol is formed which 
flows into the glass cylinder K; if the bat- 
tery is not closed the concentrated copper 
solution remains quietly standing in K, its 
greater specific gravity preventing it from 
rising higher and reaching the zinc. If, however, the circuit be 
closed, zinc is dissolved, while metallic copper is separated from 
the blue vitriol solution, and concentrated solution flows from the 
balloon C to the same extent as the blue vitriol solution in D 
becomes dilute by the separation of copper. Hence the action of 
the element remains constant for quite a long time, and of all 
the modified forms of Daniell's element consumes the least blue 
vitriol for a determined quantity of current ; however, in conse- 
quence of its great internal resistance (9.90 ohms) its current- 
strength is small. The electro-motive force of the Meidinger 
element is 0.95 volt. 

Grove, in 1839, substituted platinum for copper; the platinum 
dips in concentrated nitric acid, while the zinc cylinder stands in 
dilute sulphuric acid. The hydrogen liberated on the platinum 
is oxidized to water by the nitric acid, hyponitrous acid escaping 




GALVANIC ELEMENTS, THERMO-PILES, ETC. 49 

in the form of gas. The electro-motive force of the Grove 
element is at first double that of the Daniell element, but it soon 
abates on account of the dilution of the nitric acid by water. 
To prevent this weakening, concentrated sulphuric acid, which 
absorbs the water formed by the oxidation of the hydrogen, may 
be added to the nitric acid. Though the resistance of the Grove 
element is small (0.70 to 0.75 ohm), and its electro-motive force 
1.70 to 1.90 volts, according to the concentration of the solutions, 
it is but seldom used on account of its costliness. 

Bunsen, in 1841, replaced the expensive platinum by prisms 
cut from gas-carbon, which is still less electro-negative than 
platinum and very hard and solid so that it perfectly resists the 
action of the nitric acid. In place of the gas-carbon an artificial 
carbon may be prepared by kneading a mixture of pulverized 
coal and coke with sugar solution or syrup, bringing the mass 
under pressure into suitable iron moulds and glowing it with the 
exclusion of air. After cooling, the carbon is again saturated 
with sugar solution (others use tar, or mixtures of tar and glycer- 
ine) and again glowed with the exclusion of air, these operations 
being, if necessary, repeated once more, especially when great 
demands are made on the electro-motive force and solidity of the 
artificial carbons. 

Figs. 8, 9, and 10 show the three forms of Bunsen's elements 
most generally used. 

Fig. 8, which is the most convenient and practical form, con- 
sists of an outer vessel of glass. In this is placed a cylinder of 
zinc in which stands a porous clay cell, and in the latter the 
prism of gas-carbon. A band of copper is soldered or secured 
by means of a binding screw to the zinc cylinder, while the prism 
of gas-carbon carries the binding screw (armature), as seen in 
Fig. 8, in the upper part of which a copper sheet or wire is 
fixed for the transmission of the current. The outer vessel is 
filled with dilute sulphuric acid (1 part by weight of sulphuric 
acid of 66° Be. — free from arsenic — and 15 parts by weight of 
water), and the porous cell with concentrated nitric acid of at 
least 36° Be., or still better 40° Be., care being had that both 
fluids have the same level. 

In Fig. 9 the cylinder of artificial carbon is in the glass 
4 



50 



ELECTEO-DEPOSITION OF METALS. 



vessel, while the zinc, which, in order to increase its surface, has a 
star-like cross section, is placed in the porous clay cell. In this 
case the outer vessel is filled with concentrated nitric acid, and 
the clay cell with dilute sulphuric acid. 



Fig. 8. 



Fig. 9. 





Fig. 10. 




The form of the Bunsen element, shown in Fig. 8, is more 
advantageous, because its effective zinc surface can be kept larger. 
Fig. 10 shows a plate element, such as is chiefly used for bichro- 
mate batteries. 

The Bunsen elements are much used for electro-deposition since 
they possess a high electro- motive force (1.88 volts) and, on 
account of slight resistance (0.25 ohm) develop considerable cur- 
rent-strength. Like the Grove elements, they have the incon- 
venience of evolving vapors of hyponitrous acid, which are not 
only injurious to health, but also attack the metallic articles in 
the workshop. Wherever possible they should be placed in a box 
at such a height that they may be readily manipulated. This 
box should have means of ventilation in such a way that the air 
coming in at the lower part will escape at the top through a flue 
and carry away with it the acid fumes disengaged. It is still 
better to keep the elements in a room separate from that where 
the baths and metals are to be operated upon. Furthermore, as 
the nitric acid becomes diluted by the oxidation of the hydrogen, 
and the sulphuric acid is consumed in the formation of sulphate 
of zinc, the acids have to be frequently renewed. 

To avoid the acid vapors, as well as to render the elements 



THERMOPILES, ETC. 51 

more constant, A. Dupre has proposed the use of a 30 per cent, 
solution of bisulphate of potash in water in place of the dilute 
sulphuric acid, and a mixture of water 600 parts, concentrated 
sulphuric acid 400, sodium nitrate 500, and bichromate of potash 
60, in place of the nitric acid. 

The following method can be recommended : The outer vessel 
which contains the zinc cylinder is filled with a moderately con- 
centrated (about 30 per cent.) solution of bisulphate of potash or 
soda, and the clay cell with solution of chromic acid — 1 part 
chromic acid to 5 parts water. As soon as the electro-motive 
force of the element abates, it is strengthened by the addition of 
a few spoonfuls of pulverized chromic acid to the chromic acid 
solution. It is better to use the chromic acid in the form of 
powder, which is especially prepared for this purpose, than a 
chromic acid solution produced by mixing solution of bichromate 
of potash with sulphuric acid, the tendency of the latter to form 
crystals exerting a disturbing effect. 

In using nitric acid it is also advantageous to pour a 0.39 to 
0.78 inch thick layer of oil upon the acid to decrease the vapors. 

The binding screws which affect the metallic contacts must of 
course be frequently inspected and cleaned, which is best done by 
means of a file or emery paper. It is advisable to place a piece 
of platinum sheet between the binding surface of the carbon 
armature and the carbon in order to avoid the acid rising through 
the capillarity of the carbon from acting directly upon the arma- 
ture (generally brass or copper). To prevent the acid from 
rising, the upper portion of the carbons may be impregnated with 
paraffine. For this purpose the carbons are placed f to 1 inch deep 
in melted paraffine and allowed to remain 10 minutes. On the 
sides where the armature comes in contact with the carbon, an ex- 
cess of paraffine is removed by scraping with a knife blade or rasp. 

Manipulation of Bunsen elements. — Before using the elements 
the zinc cylinders should be very carefully amalgamated according 
to one of the methods given on p. 45. The nitric acid need not 
be pure, the crude commercial acid suffices, but it should be as con- 
centrated as possible and show at least 36° Be. For the prisms 
it is best to take carbon produced in gas-houses using coal without 
the addition of brown coal, the electro- motive force of the latter 



52 ELECTRO-DEPOSITION OF METALS. 

being smaller. If artificial carbon is employed it should be ex- 
amined as to its suitability, the non-success of the plating process 
being frequently attributed to the composition of the bath, when in 
fact it is due to the bad carbons of the elements. In order to avoid 
an unnecessary consumption of zinc and acid the elements are taken 
apart when not in use, for instance, over night. Detach the brass 
armature of the carbon prism and lay it in water to which some 
chalk has been added, lift the carbon from the clay cylinder and 
place it in a porcelain dish or earthenware pot ; empty the nitric acid 
of the clay cell into a bottle provided with a glass stopper ; place the 
clay cell in a vessel of water, and finally take the zinc cylinder from 
the dilute sulphuric acid and place it upon two sticks of wood laid 
across the glass vessel to drain off. In putting the elements to- 
gether the reverse order is followed, the zinc being first placed in 
the glass vessel and then the carbon in the porous clay cell. The 
latter is then filled about three-quarters full with used nitric acid, 
and fresh acid added until the fluid in the clay vessel stands at a 
level with that in the outer vessel. The cleansed brass armature 
is then screwed upon the carbon prism. Finally add to the dilute 
sulphuric acid in the outer vessel a small quantity of concentrated 
sulphuric acid saturated with mercury salt. 

It is advisable to have at least a duplicate set of porous clay 
cells, and in putting the elements together to use only cells which 
have been thoroughly soaked in water. The reason for this is as 
follows : The nitric acid fills the pores of the cell, and finally 
reaching the zinc of the outer vessel causes strong local action and 
a correspondingly rapid destruction of the zinc. It is, therefore, 
best to change the clay cells every day, allowing those which have 
been in use to lie in water the next day with frequent renewal of 
the water. For the same reason the nitric acid in the clay cell 
should not be at a higher level than the sulphuric acid in the 
outer vessel. 

When the Bunsen elements are in steady use from morning till 
night, the acids will have to be entirely renewed every third or 
fourth day. The solution of sulphate of zinc in the outer vessel 
is thrown away, while the acid of the clay cells may be mixed 
with an equal volume of concentrated sulphuric acid, and this 
mixture be used as a preliminary pickle for brass and other 
copper alloys. 



GALVANIC ELEMENTS, THERMO-PILES, ETC. 



53 



The Leclanche element (zinc and carbon in sal ammoniac solu- 
tion with manganese peroxide as a depolarizator) need not be 
further mentioned, it being not adapted for regular use in electro- 
plating. It is in very general use for electric bells, its great 
recommendation being that when once charged, it retains its 
power without attention for several years. 

Lallande and Chaperon have recently introduced a copper 
oxide element shown in Fig. 11, which possesses several advan- 
tages. It consists of the outer vessel G of cast-iron or copper 
which forms the negative pole surface, and to which the wire 

Fig. 11. 




leading to the anodes is attached, and a strip of zinc, Z, coiled in 
the form of a spiral which is suspended from an ebonite cover 
carrying a terminal connected with the zinc. The hermetical 
closing of the vessel G by the ebonite cover, is effected by means 
of three screws and an intermediate rubber plate. Upon the 
bottom of the vessel G is placed a 3 to 4 inch deep layer of 
copper oxide, 0, and the vessel is filled with a solution of 50 
parts of caustic potash in 100 of water. When the element is 
closed, decomposition of water takes place, the oxygen which 
appears on the zinc forming with the latter zinc oxide which 
readily dissolves in the caustic potash solution, while the hydro- 



54 ELECTRO-DEPOSITION OF METALS. 

gen is oxidized with the simultaneous reduction of copper oxide 
to copper. When the element is open, i. e., the circuit not closed, 
neither the zinc nor the copper oxide is attacked, and hence no 
local action nor any consumption of material takes place. The 
electro-motive force of this element is 0.98 volt, and its internal 
resistance very low. It is remarkably constant and is well adapted 
for electro-plating purposes by using two of them for one Bunsen 
element. The following rides have to be observed in its use. It 
is absolutely necessary that the ebonite cover should hermetically 
close the vessel G, as otherwise the caustic potash solution would 
absorb carbonic acid from the air, whereby carbonate of potash 
would be formed which would weaken the exciting action of the 
solution. Further the vessel G forming the one pole must be 
insulated from the other as well as from the ground as otherwise 
a loss of current or defective working would be the consequence. 

The elements of Marie Davy, Niaudet, Duchemin, Sturgeon, 
Trouville, and others, being of little value for practical use, may 
be passed over. 

Duns's potash element. — On account of its great electro-motive 
force (1.6 volts) and slight internal resistance this element would 
be well adapted for electro-plating purposes, if depolarization 
would take place more rapidly than is actually the case. Its 
construction is as follows : In a glass vessel stands a carbon 
cylinder closed below, and in the centre of the carbon cylinder a 
clay cell. The space between the clay cell and the interior wall 
of the carbon cylinder is filled f full with pieces of carbon. In 
the clay cell stands an amalgamated strip of zinc or zinc cylinder 
to which the conducting wires are soldered, the place of soldering 
as well as the wire as far as it comes in contact with the fluid, is 
covered with gutta percha. The edge of the carbon cylinder is 
coated with paraffine and carries the pole binding screw. The 
filling of the element is effected by laying potassium permanga- 
nate in crystals upon the layer of carbon between the clay and 
carbon cylinders, and pouring a solution of 1 part of pure caustic 
potash in 2 of water into the clay cell, the pouring being continued 
until the fluid runs over the clay cell upon the potassium perman- 
ganate and the layer of carbon, and finally fills the outer vessel 
up to about the breadth of two fingers from the edge. The 
action of the element is as follows : When the element is closed 



55 

decomposition of water takes place, the oxygen combining with the 
zinc to zinc oxide, which is dissolved by the potash lye, while the 
hydrogen is oxidized on the positive pole by the potassium per- 
manganate. The latter, to be sure, contains much oxygen, and 
acts very energetically, but as it diffuses very slowly, depolariza- 
tion, i. e., the removal of the hydrogen is not so quickly effected 
as, for instance, in the Bunsen element, where the nitric acid 
rapidly diffuses. Hence with a slight external resistance, for 
instance, baths where the element has to furnish large quantities 
of current, the tension sinks very rapidly and with it the current- 
strength, and, therefore, the element is only suitable for electro- 
plating purposes when a current need only for a short time be 
produced, but not for permanent work. In the first case it offers 
the advantage of being always ready for use, evolving no vapors, 
and when not in use consuming no material. It is prudent to 
protect this element from the action of the carbonic acid of the 
air by a close cover. 

We will add a few words in regard to the so-called dipping or 
bichromate batteries. For our purposes it will suffice to mention 
the Bunsen bichromate battery. For constructive reasons only 
one fluid is used into which the zinc as well as the carbon plates 
dip, a solution of chromic acid prepared by dissolving 10 parts 
of bichromate of potash and \ part of mercuric sulphate in 100 
parts of water, and adding 18 parts of pure concentrated sulphuric 
acid being employed. More advantageous is a solution of chromic 
acid in the form of powder in water in the proportion of 1 : 5, 
for the same reason as given on p. 51. 

Fig. 12 shows a bichromate battery as constructed by Fein. 
Into the 6 element-vessels standing in two rows in the wooden 
box M, dip the zinc and carbon plates which are secured to wooden 
cross pieces provided with handles and may be maintained at any 
desired height by the notch e in the standards G. According to 
the current-strength required, the plates are allowed to dip in 
more or less deeply. 

Fig. 13 shows a bichromate battery as constructed by Keiser & 
Schmidt. 

In using the above-mentioned chromic acid solution, which has 
already been recommended by Bunsen, the elements at first 
develop a very strong current, which, however, in a compara- 



56 



ELECTRO-DEPOSITION OF METALS. 



tively short time becomes weaker and weaker. The current- 
strength can be increased by adding at intervals a few spoonfuls 

Fig. 12. 




Pig. 13. of pulverized chromic acid to the chro- 

mic acid solution, which, however, finally 
remains without effect, when the battery 
has to be freshly filled. Hence, these 
batteries are not suitable for electro- 
plating operations requiring a constant 
current for some time. 

For temporary use, for instance, by 
gold-workers and others, for gilding or 
silvering small articles, the bottle-form 
of the bichromate element (Fig. 14) may 
be advantageously employed. In the 
bottle A two long strips of carbon united 
above by a metallic connection are fastened parallel to one another 
to a vulcanite stopper, and are there connected with the binding 
screw ; these form the negative element, and pass to the bottom 




GALVANIC ELEMENTS, THERMOPILES, ETC. 



57 



of the bottle ; between them is a short thick strip of zinc attached 
to a brass rod passing stiffly through the centre of the vulcanite 
cork, and connected with the binding screw. The zinc is entirely 
insulated from the carbon by the vulcanite, and may be drawn 
out of the solution by means of the brass rod as soon as its ser- 
vices are no longer required. 

In Stoehrer's battery (Fig. 15) two acids, dilute sulphuric acid 
and concentrated nitric acid, are used. The porous clay cell is 



Fig. 14. 



Fig. 15. 





entirely omitted, the massive carbon cylinders K K, etc., being 
provided with a cavity reaching almost to the bottom which is 
filled with sand and nitric acid. The contact of the carbon and 
zinc cylinders is prevented by glass beads inserted in the first. 



B. Thermopiles. 

Though thermo-piles are only used in isolated cases for electro- 
plating operations, for the sake of completeness their nature and 
best known forms will be briefly mentioned. 



58 



ELECTRO-DEPOSITION OF METALS. 



Seebeck, in 1823, observed that electricity is developed when 
two metals soldered together are unequally heated at their point 
of junction ; thus, as electricity can be converted into heat, heat 
can also be converted into electricity. 

Noe's pile (Fig. 16) consists of a series of small cylinders com- 
posed of an alloy of 36 J parts of zinc and 62 J parts of antimony 

Fig. 16. 





for the positive element, and stout German silver as the negative 
element. The junctions of the elements are heated by small gas 
jets, and the alternate junctions are cooled by the heat being con- 
ducted away by large blackened sheets of thin copper. A pile of 
twenty pairs have an electro-motive force of 1.90 volts. 

Clamond's thermo-pile (Fig. 17) consists of an alloy of 2 parts 
antimony and 1 of zinc for the negative metal, while for the posi- 
tive element ordinary tinned sheet-iron is employed, the current 
flowing through the hot junction from the iron to the alloy. To 
insure a good contact between the two metals a strip of tin-plate 
is bent into a narrow loop at one end. This portion is then placed 
in a mould and the melted alloy poured around it, so that it is 
actually imbedded in the casting. The pile shown in the illustra- 
tion consists of five series one placed above the other ; each series 
has ten elements grouped in a circle, and is insulated from the 
succeeding series by a layer of cement composed of powdered 



GALVANIC ELEMENTS, THERMOPILES, ETC. 



59 



asbestos moistened with a solution of potassium silicate. With 
the consumption of about 6J cubic feet of gas per hour, such a 

Fig. 17. 




pile precipitates 0.7 oz. of copper, which corresponds to an inten- 
sity of about 17 amperes. 



C. Magneto- and Dynamo- Electric Machines. 

The principle of induction upon which the dynamo-electric 
machines are based has been explained on p. 35 . Faraday, in 
1831, made the important discovery that by moving a coil of 
wire in the presence of a magnet a current of electricity was 
generated in the coil, or vice versa, by moving the magnet and 
holding the coil stationary a like result was obtained; thus a 
current of electricity was produced, either by moving a wire in 
the presence of a stationary magnet, or by moving a magnet in 
the presence of a stationary wire. 

The intensity of the current thus obtained depends on the 
strength of the magnet, and on the velocity with which the mag- 
net or coil is moved through the magnetic field. Upon these 
simple facts is based the whole of the recent important develop- 
ments of electrical science. 

Before describing the various attempts made to devise some 



60 ELECTRO-DEPOSITION OF METALS. 

mechanical means whereby the different elements which produced 
the temporary or momentary currents could be combined, so as 
to collect them, and cause them to flow in rapid succession, the 
one after the other, without interruption, it will be well to remem- 
ber that the necessary elements for producing these induced elec- 
tric currents are simply a bar magnet and an insulated coil of 
wire. It will also be well to remember that every magnet, no 
matter what its form, has two poles — a north and south pole — 
and each of these poles exerts a certain influence in its immediate 
neighborhood, the space thus affected being termed the magnetic 
field or the region of the lines of force. The attraction or magnetic 
force of these lines varies as the inverse ratio of the square of the 
distance ; therefore, the nearer the magnet the greater the inten- 
sity of the magnetism. Faraday proved that these lines, which 
he designated lines of force, showed by their position the direc- 
tion of the magnetic force, and by their number its intensity. 
By passing a coil of wire through this field, so as to cause it to 
cut, as it were, a number of these lines of force, a current of 
electricity will be generated in the coil ; and if it can be so 
arranged that a number of these coils will pass in rapid succession 
through the magnetic field, we shall have a series of impulses 
giving us practically a continuous stream of electricity. 

Thus a magneto-electric or dynamo-electric machine is simply 
a mechanical arrangement of certain elements, whereby the energy 
of motion is converted into electrical energy through the medium 
of magnetism. The number of such machines is legion. In 
each case the arrangement of the armature of the magnets, and 
of the commutators, is varied, but the principle is always the 
same — coils of insulated wire being caused to cut through mag- 
netic fields, as explained. 

The first attempt to devise an electrical machine was made by 
Pixii, who, in 1832, constructed a machine consisting of a perma- 
nent magnet, which he caused to revolve in front of the iron cores 
of a pair of bobbins, forming an electro-magnet. This invention 
was improved by other workers in the field of science, especially 
by Saxton and Clarke, both of whom succeeded in producing 
very useful electric generators, in which the mechanical arrange- 
ment is the reverse of that in Pixii's — i. e. } the magnets are fixed 



GALVANIC ELEMENTS, THERMO-PILES, ETC. 61 

and the coils of wire movable. And it is on this plan that all the 
subsequent machines have been constructed, as affording better 
results than where the coils are stationary and the magnets mov- 
able. 

A great improvement was made in 1857, by Dr. W. Siemens, 
of Berlin. It consisted essentially in a new form of armature 
which owing to its simplicity and cheapness is still used for many 
purposes, especially for electro-plating and laboratory work. It 
is composed of a cylinder of iron in which deep longitudinal 
grooves are cut resembling in section the letter H. In these 
grooves is wound lengthwise a single coil of wire, the two ends 
of which being joined to a split tube of copper on the axle, form 
the commutator from which the current is taken off by brushes 
or springs rubbing against it. By this longitudinal armature the 
advantage is gained of cutting the greatest number of lines of 
force when rotated between the poles of a series of adjacent 
magnets. 

One of the most important inventions for the construction of 
electrical machines is the ring conductor by Pacinotti (1860). 
With the use of this ring conductor continual currents of the 
same direction can be produced without the assistance of a com- 
mutator. 

Next in order comes the important discovery made simulta- 
neously, but independently, by Dr. W. Siemens and Sir C. Wheat- 
stone — a discovery which marks the transition of the magneto elec- 
tric machine to that type most in practice at present — the dynamo 
machine, called for convenience the dynamo. What Dr. Siemens 
and Sir C. Wheatstone discovered was this : That a current of 
electricity could be generated in the coils on the armature by the 
feeble residuum magnetism in the iron cores of the electro-mag- 
nets, and that by passing this feeble current round the magnets, 
their magnetism would be strengthened, which in turn would 
produce a stronger current in the armature, and this current 
would again react on the magnets rendering them more powerful, 
this action going on until the limit of saturation is attained ; for 
it must be understood that this mutual accumulation cannot go on 
indefinitely, the magnetism in the iron cores cannot be intensified 
beyond a certain point, and this point depends on and is con- 



62 ELECTRO-DEPOSITION OF METALS. 

trolled by the scientific conditions on which the machine is con- 
structed. 

Machines constructed on this principle are called, as stated, 
dynamo machines, to distinguish them from those previously used 
in which the magnets were permanently magnetized, thus causing 
the division of electric generators into two great classes, viz., 
magneto and dynamo machines, which are subdivided into two 
varieties — one called the continuous current machine furnishing 
currents in the same direction, and the other the alternate current 
machine wherein the current is rapidly reversed, or its direction 
changed many times a minute. 

An essential difference between continuous and alternate cur- 
rent machines is that the former may be self-exciting, whereas the 
latter must have a separate exciter or must be a magneto machine. 
The cores of the electro-magnets, it may be mentioned, are of 
cast-iron, in which there is always a feeble residual magnetism. 
It is also easier to magnetize iron than steel, although, when the 
latter is once magnetized, it retains its magnetism for an indefinite 
period. 

It is not within the province of this work to describe in detail 
all the forms of dynamos, it being sufficient for our purposes to 
discuss those which are adapted to and are used for electro-plating 
uses. If we mention the Gramme machine first, it is not because 
it is superior to other machines, but because M. Gramme, its 
inventor, was the first to utilize the idea suggested by Dr. 
Pacinotti of using an iron ring as a revolving electro-magnet, 
which in place of having fixed revolving poles, had poles which 
travelled continuously through the Avhole circumference of the 
ring. 

The cut (Fig. 18) shows the Gramme armature in such a way as 
to allow its construction to be seen. The core or centre of the 
ring consists of a bunch of soft iron wires; the wire system 
wound about the core is formed of different spools, the initial 
wire of which is soldered to the terminal wire of the neighboring 
spool, so that all the spools of the ring form a single uninterrupted 
conductor. The soldered places lie all on one side of the ring, 
and are fastened to flat copper strips bent at right angles and 
insulated from one another by a non-conductive mass which 



GALVANIC ELEMENTS, THERMO-PILES, ETC. 



63 



forms the commutator through which the axle passes. The 
armature revolves between the poles of the electro-magnets 

Fig. 18. 




secured to the sides of the machine as shown in Fig. 19. As 
the ring is revolved a current is generated and flows out with 
every change in its position. The current so made is carried out 



Fig. 19. 




64 



ELECTRO-DEPOSITION OF METALS. 



by wire brushes which press upon the terminal plates of the wires 
in the ring. 

In the modern Gramme dynamos (Fig. 20) for galvano-plastic 
purposes, which have to furnish a considerable volume of current of 



Fig. 20. 




slight electro-motive force, the inducting magnets are surrounded 
by broad copper bands instead of being wound about with copper 
wire, and the armature is built up of stout copper rods, because 
the less resistance the copper windings have the greater the 
volume of current which is produced, while vice versa the tension 
increases with their resistance. Hence, machines for electro- 
plating purposes which have to furnish quantities of current of 
slight tension are wound about with stout copper wire, while 
those for illuminating purposes which must furnish currents of 
high tension are wound about with thin copper wire. For this 
reason machines constructed for galvano-plastic use., and for 
nickeling, coppering, brassing, etc., are not suitable for illumi- 



GALVANIC ELEMENTS, THERMO-PILES, ETC. 



65 



nating purposes, and vice versa, machines constructed for electric 
lighting cannot suitably be employed for galvanic purposes. 

A disadvantage of the Gramme machine is that only the portion 
of the copper windings on the outside of the ring conductor is in 
the magnetic field of the poles of the electro-magnets, so that only 
a comparatively small portion of the inductor is exposed to the 
inductive action of the magnets. Hence, in order to furnish cor- 
respondingly strong currents, the ring inductor must revolve very 
rapidily, the three numbers of Gramme machines mostly employed 
for galvano-plastic purposes making in fact from 1500 to 2000 
revolutions per minute, whereby the bearings are more rapidly 
worn out than with machines running at less speed and, besides, 
more power is consumed. 

This evil led S. Schuckert, of Nurenberg, to the construction of 
a machine in which a Hat ring is successfully used as an inductor 

Fisr. 21. 




which stands almost entirely under the inductive influence of the 
electro-magnets. Schuckert's flat ring machine is shown in Fig. 
21. The core of the machine consists of thin sheet ribbands 
insulated one from another, whereby greater solidity is attained ; 
the commutator and brushes are similar to those of the Gramme 
machine. The number of revolutions varies for the different 
5 



66 



ELECTEO-DEPOSITION OF METALS. 



sized machines from 500 to 1500 per minute. It is almost noise- 
less in action and is exceedingly well constructed. The formation 
of sparks on the contact-surface of the brushes with the commu- 
tator is scarcely perceptible, which secures the durability of the 
latter. 

Fein, of Stuttgart, has endeavored to overcome the defect of the 
Gramme machine in a different manner. In these machines the 
polar extensions of the magnets M and M f (Fig. 22) are elonga- 
ted to a sort of a drum, A A, which leads into the interior of the 
inductor ring, whereby the greater portion of the windings is also 
brought into the magnetic fields of the electro-magnets. 

Fig. 22. 




Closely resembling the Gramme machine in its general outline, 
but differing materially in construction and action, is that known 
as the Brush dynamo. Its armature though consisting of a ring 
like that of Gramme's, is, however, differently built up. At 
intervals, around the ring, a number of transverse grooves are 
formed, in which are wound the coils or bobbins, all in the same 
direction ; and instead of forming a continuous circuit, as in the 
Gramme, each diametrically opposite pair of coils is joined to 
each other by one end of each coil, while the other ends of the 
pair (i. e., the ends conveying the current) are connected to the 



GALVANIC ELEMENTS, THERMOPILES, ETC. 



67 



commutator. Fig. 23 illustrates the ring, showing the opposite 
coils joined up as described. Four coils are removed to show its 

Fig. 23. 




construction. A series of deep concentric grooves will be ob- 
served formed in the ring, their object being to reduce the mass 
of iron, and also to facilitate ventilation, thereby preventing the 
tendency to heat while the machine is working. 




Fig. 24 represents the complete Brush machine set in motion 
by a Brotherhood motor with three cylinders, the usual speed of 
the machine being about 750 revolutions per minute. 



68 



ELECTRO-DEPOSITION OF METALS. 



The machines built by Siemens & Halske, in which the cylin- 
der-inductor invented by Hofner-Altenbeck is used, show a differ- 
ent construction from those previously described. A detailed 
explanation of the cylinder-inductor would lead too far. It con- 
sists of a hollow iron cylinder, which revolves with the shaft, 
and about which the wires are wound parallel to the revolving 
axis in such a manner that no wire-windings are in the interior 
of the core (cylinder). The wire spirals wound about the cylin- 
der are divided into sections, which are so connected one with an- 
other as to form a single connected wire conductor. The terminal 
wires of the separate sections are connected to the segments of the 
commutator, so that both the currents generated in the wire sys- 
tem always meet from an opposite direction in two portions of 
the commutator opposite to one another. The commutator is 
constructed according to the Gramme system, and has, of course, 
as many segments as there are sections wound upon the cylinder. 
A real advantage of this machine is that the greater portion of 
the wire-windings of the cylinder-inductor is in the magnetic field. 

Fig. 25. 




Fig. 25 shows a Siemens & Halske magneto-electric machine 
with cylinder inductor. 

Two series of 25 Y-shaped magnets each, are placed above and 
below, so that their poles of a similar name are opposite to one 



THERMO-PILES, ETC. 69 

another, the poles of a similar name of the upper and lower 
magnets being connected one with another by arched pieces of 
soft iron. In the space thus formed between the upper and lower 
magnets, the cylinder-inductor revolves, the generated currents 
being carried away from the commutator by the brushes R and R f . 
In Siemens & Halske's dynamo-electric machines for electro- 
metallurgical purposes (Fig. 26), the plate magnets are wound 

Fig. 26. 




about with square copper rods, in smaller machines with stout 
copper wire, while instead of spirals the inductor carries copper 
ribbands, which are connected with the commutator by suitably 
bent pieces. 

Fig. 27 represents the Weston machine, which is much used 
in this country. Being of small dimensions, of compact form, 
and yielding an abundant current, it is well adapted to the wants 
of the electro-plater. An iron ring or cylinder attached to an 
iron base forms the outer shell of the machine. From the inte- 
rior of this cylinder, and projecting radially towards the centre 
of the apparatus, are arranged a number of magnets (usually five), 
which consist of a core of iron to which are fastened a number of 
thin tempered steel plates, and they are wrapped with insulated 
copper wire and so connected that the poles shall be alternately 
north and south. In the central space left between the inward 
ends of these magnets is arranged a shaft carried by bearings, 



70 ELECTRO-DEPOSITION OF METALS. 

which, to secure greater strength and perfect alignment, are cast 
on the iron disks or heads which are accurately fitted and bolted 
to the ends of the cylinder. To the shaft is secured a series of 
armatures made in segments. The armatures are of iron and also 

Fig. 27. 



wrapped with wire. When revolved the outwardly projecting 
ends of these armatures will pass closely to, but without touching, 
the inwardly projecting ends of the magnets. The commutator 
is made in two pieces and requires but two springs to carry the 
currents from all the armatures. These springs or brushes are 
clamped in sockets projecting from the front disk of the cylinder. 
An automatic switch or governor is attached to this machine for 
the purpose of preventing it from reversing by the polarization 
of the electrodes. 

Fig. 28 shows the Krottlinger machine constructed by Krott- 
linger, of Vienna. It consists of a strong iron base, P, from 
which rise two short cylindrical electro-magnets, M M, which 
have a semi-circular shaft on the upper end, N, and closely 
embrace the ring JR. The standards L are cast in one piece with 
the base P, and carry the bearings W W. The core of the ring 
R consists of separate disks of cast iron arranged alongside one 
another upon the shaft so as to form a massive cylinder which is 



GALVANIC ELEMENTS, THERMO-PILES, ETC. 



71 



wound about with stout copper wire. The inductive spools of 
the ring are connected by means of screws with the phosphor- 
bronze plates of the commutator C. In this dynamo the current 
generated in the ring does not pass first through the electro-magnets, 



Fisr. 28. 




and then as working current into the conductor, but the greater 
portion passes as working current from the brushes B B into the 
conductor to the baths, while the other comparatively smaller 
portion of current passes through the wrappings of the electro- 
magnets M M, and excites them. As in Schuckert's machines a 
regulator with resistance coils may be inserted in the circuit of 
the current which allows of the generation of the current being 
controlled within quite wide limits, as may be desired. The 
advantages of this dynamo consist in the large masses of iron of 
short length with a large cross-section of the cores of the electro- 
magnets, the standards and base being made in one piece, and the 
durable iron core of the ring, the formation of sparks is slight. 

The Lahmeyer dynamo shown in Figs. 29, 30, and 31 in cross- 
section, open side view and perspective exterior view, fulfils the 
three principal conditions of a good dynamo, viz., great useful 
effect, discharge of the current without sparks, and solidity of 
construction. Opposite to the drum-anchor or drum-inductor of 
the machine stand horizontally two short and stout electro-magnet 



72 



ELECTRO-DEPOSITION OF METALS. 



cores, whose ends averted from the anchor are connected by a thick 
iron frame carried above and below around the windings. This 
electro-magnet frame is made of soft cast-iron in one piece with 
the base of the machine, so that no resistance is offered to the 



Fig. 29. 



Fig. 30. 





lines of force by a joint, while the large iron cross-sections also 
give rise to but a slight magnetic resistance. 

The magnetic field of the Lahmeyer machine must be consid- 
ered as a magnetic circle in so far as the lines of force which are 
generated by the spools in the iron everywhere contiguous to 
them, pass together through both spools, and only ramify outside 
of them in the re-conducting plates B B r . By this favorable 
disposition, a current of slight strength passing through the 
wrappings of the electro-magnets produces a strong excitation of 
the latter. 

The anchor has the shape of the Siemens cylinder, but is 
composed of disks of thin, white sheet-iron insulated one from 
the other by paper. Several segments of vulcanized fibre, two of 
which form the face, serve for holding the wrappings of the 
anchor. The latter consists of a single layer of stout copper 
wire, and this, in conjunction with the symmetrical disposition 
which excludes the scattering of the lines of force as much as 
possible, effects a discharge of the current without sparks. The 
space visible in the side view is closed by perforated plates secured 
by screws as seen in Fig. 31. This is a further advantage of the 
machine in as far as all sensitive parts are protected from external 
injuries. Like all cylinder or drum dynamos, the Lahmeyer 



GALVANIC ELEMENTS, THERMOPILES, ETC. 



73 



dynamo requires a large number of revolutions per minute, but 
with the slight weight of the anchor, and the solid construction 
of the bearings, there is but little danger of the rapid wearing 
out of the latter. 



Fia:. 31. 




Detailed descriptions of other machines such as the Miiller, 
Mather, Elmore, Biirgin, Gulcher, etc., would needlessly lengthen 
this chapter. The great impulse which the art of electro-plating 
has within the past decade received is largely due to the great 
improvements that have within this period been made in the con- 
struction of dynamo-electric machines, by which mechanical energy 
generated by the steam-engine or other convenient source of power 
may be directly converted into electrical energy. Without dynamos 
it would be impossible to electro-plate large parts of machines, 
building ornaments, etc., which are thus protected from the influ- 
ence of the weather. They may safely be credited with having 
called into existence an important branch of the electro-plating art, 
viz., nickel-plating and especially the nickel-plating of zinc sheets 
as well as sheets of copper, brass, steel and tin, which would have 
been impossible if the manufacturer had to rely upon the genera- 
tion of the electric current by batteries. The latter, at the very 
best, are troublesome to manage ; they only give out their full 
power when freshly charged, and as the chemical actions upon 
which they rely for their power progress, they deteriorate in 
strength and require frequent additions of acids and salts to be 
freshly charged, and their use demands constant vigilance and 



I 



74 ELECTRO-DEPOSITION OP METALS. 

attention. Even when working on a small scale it is cheapest to 
procure a small gas or other motor for driving a small dynamo, 
the lathes, and grinding and polishing machines. 

To make it possible for the manufacturer of dynamos to sug- 
gest the most suitable machine, the following data should be sub- 
mitted to him : — 

1. Variety, size and number of the baths which are to be fed 
by the machine. 

2. The average surface of the articles in the bath, or their 
maximum surface, and the metals of which they consist. 

3. Whether at one time many and at another time few articles 
are suspended in the bath. 

4. The distance at which the machine can be placed from the 
baths. 

5. The power at disposal. 



ELECTRO-PLATING ESTABLISHMENTS. 75 



IV. 

PRACTICAL PART. 



CHAPTER IY. 

ARRANGEMENT OF ELECTRO-PLATING ESTABLISHMENTS 
IN GENERAL. 

Although rules valid for all cases cannot be given, because 
modifications will be necessary according to the size and extent 
of the establishment, the nature of the articles to be electro-plated 
and the method of the process itself, there are, nevertheless, cer- 
tain main features which must be taken into consideration in 
arranging every establishment, be it large or small. Only rooms 
with sufficient light should be used, since the eye of the operator 
is severely taxed in judging whether the articles have been thor- 
oughly freed from fat, in recognizing the different tones of color, 
etc. A northern exposure is especially suitable, since otherwise 
the reflection caused by the rays of the sun may exert a disturb- 
ing influence. For large establishments the room containing the 
baths should, besides side-lights, be provided with a sky-light, 
which, according to the location, is to be protected by curtains 
from the rays of the sun. 

Due consideration must be given to the frequent renewal of the 
air in the rooms. It often cannot be avoided that the operations 
of pickling, etc., must be carried on in the same room in which 
the baths are located. Especially unfavorable in this respect are 
smaller establishments working with batteries, in which the vapors 
evolved from the latter are added to the other vapors and render 
the atmosphere injurious to health. Hence, if possible, rooms 
should be selected having windows on both sides, so that by 
opening them the air can at any time be renewed, or the baths 
and batteries should be placed in rooms provided with a chimney ; 



76 ELECTRO-DEPOSITION OF METALS. 

by cutting a hole of sufficient size in the chimney near the ceiling 
of the room the discharge of injurious vapors will in most cases 
be satisfactorily effected. 

To those working with Bunsen elements, it is recommended to 
place them in a closet varnished with asphalt or ebonite lacquer, 
and provided with lock and key. The upper portion of the closet 
should communicate by means of a tight wooden flue with a 
chimney or the open air. 

Since the baths work with greater difficulty, slower and more 
irregular below a certain temperature, provision for the sufficient 
heating of the operating rooms must be made. Except baths 
for hot gilding, platinizing, etc., the average temperature of the 
galvanic solutions should be from 64.5° to 68° F., at which they 
work best; it should never be below 59° F. for reasons to be 
explained later on. Hence, for large operating rooms such heat- 
ing arrangements must be made that the temperature of the baths 
cannot fall below the minimum even during the night, otherwise 
provision for the ready restoration of the normal temperature at 
the commencement of the work in the morning has to be made. 
Rooms heated during the day with waste steam from the engine, 
generally keep the baths during the winter — the only season of the 
year under consideration — so that they show in the evening a tem- 
perature of 64.5° to 68° F., and if the room is not too much 
exposed, the temperature, especially of large baths, will only in 
rare cases be below 59° F. For greater security the heating pipes 
may be placed in the neighborhood of the baths ; if this should 
not suffice to protect the baths from cooling off too much, it is 
advisable to locate in the operating room a steam conduit of 
small cross-section fed from the boiler and to pass steam for 
a few minutes through a coil of metal indifferent to the galvanic 
solution suspended in the bath. In this manner baths of 1000 
quarts, which, on account of several days' interruption in the 
operation had cooled to 36° F., were in ten minutes heated to 
68° F. For smaller baths it is better to bring a small portion of 
them in a suitable vessel to the boiling point, over a gas flame, 
and adding it to the cold bath, and if after mixing, the tempera- 
ture of the bath is still too low, repeating the operation. 

Another important factor for the operating rooms is the con- 



ELECTRO-PLATING ESTABLISHMENTS. 77 

venient renewal of the waters required for rinsing and cleansing. 
Without water the electro-deposition of metals is impossible ; the 
success of the process depends in the first place on the careful 
cleansing of the metallic articles to be electro-plated, and for that 
purpose water, nay much water, hot and cold water, is required 
as will be seen in the " preparation of the articles." Large estab- 
lishments should, therefore, be provided with pipes for the admis- 
sion and discharge of water, one conduit terminating as a rose 
over the table where the articles are freed from grease. In 
smaller establishments, where the introduction of a system of 
water-pipes would be too expensive, provision must be made for 
the frequent renewal of the cleansing water in the various vats. 

In consequence of rinsing and transporting the wet articles to 
the baths much moisture collects upon the floor of the operating 
rooms. The best material for floors of large rooms is asphalt, it 
being, when moist, less slippery than cement ; a pavement of 
brick or mosaic laid in cement is also suitable, but has the disad- 
vantage of cooling very much. The pavement of asphalt or 
cement should have a slight inclination, a collecting basin being 
located at the lowest point, which also serves for the reception of 
the rinsing water. Wood floors cannot be recommended, at least, 
not for large establishments, since the constant moisture causes 
the wood to rot ; however, where their use cannot be avoided, the 
places where water is most likely to collect, should be strewn with 
sand or saw-dust, frequently renewed, or the articles when taken 
from the rinsing water or bath be conveyed to the next operation 
in small wooden buckets or other suitable vessels. 

The operating room should be of such a size as to permit the 
convenient execution of the necessary manipulations. Of course, 
no general rule can be laid down in this respect, as the size of the 
room required depends on the number of the processes to be 
executed, the size and number of articles to be electro-plated 
daily, or within a certain time, etc. However, there must be 
sufficient room for the batteries or dynamo for the various baths, 
between which there should be a passage-way at least twenty inches 
wide for the table where the articles are freed from grease, for the 
lye kettle, hot-water reservoir, saw-dust receptacle, tables for 
tying the articles to hooks, etc. 



78 ELECTRO-DEPOSITION OF METALS. 

The rooms used for grinding, polishing, etc., also require a good 
light in order to enable the grinder to see whether the article is 
ground perfectly clean, and all the scratches from the first grind- 
ing are removed. Where iron or other hard metals are ground 
with emery, it is advisable to do the polishing in a room sepa- 
rated from the grinding shop by a close board partition, because 
in the preparatory grinding with emery, which is done dry, with- 
out the use of oil or tallow, the air is impregnated with fine 
particles of emery, which settle upon the polishing disks and 
materials, and in polishing soft metals cause fine scratches and 
fissures injurious to the appearance of the articles and difficult to 
remove by polishing. Hence, all operations requiring the use of 
emery, or coarse grinding powders, should be performed in the ac- 
tual grinding-room, as well as the grinding upon stones and scratch- 
brushing by means of rapidly revolving steel scratch-brushes 
of iron castings. Articles already electro-plated are, of course, 
scratch-brushed in the plating-room itself, either on the table 
used for freeing the articles from grease, or on a bench especially 
provided for the purpose. In the polishing room are only placed 
the actual polishing machines, which by means of rapidly revolving 
disks of felt, flannel, etc., and the use of polishing powders, or 
polishing compositions, impart to the articles the final lustre before 
and after electro-plating. The formation of dust in the polish- 
ing rooms is generally over-estimated ; it is, however, sufficiently 
large to render their separation by a close partition from the 
electro-plating room necessary, otherwise the polishing dust might 
settle upon the baths and give rise to various disturbing phe- 
nomena. In rooms in which large sheet-surfaces are polished 
with Vienna lime, as, for instance, nickeled sheets, the dust often 
seriously affects the health of the polishers, especially in badly 
ventilated rooms, and in such cases it is advisable to provide an 
effective ventilator. If this cannot be done, wooden frames cov- 
ered with packing cloth, placed opposite the polishing disks, render 
good service ; the packing cloth by being frequently moistened 
retaining a large portion of the polishing dust. 

For grinding lathes requiring the belt to be thrown off in order 
to change the grinding, it is best to place the transmission carrying 
the belt pulleys at a distance of about three feet from the floor, 



ELECTRO-PLATING ESTABLISHMENTS. 79 

for lathes with spindles outside the bearings the transmission may 
be on the ceiling or wall. The revolving direction of the prin- 
cipal transmission should be such as to render the crossing of the 
belts to the grinding and polishing machines unnecessary, other- 
wise the belts on account of the great speed will rapidly wear out. 

ELECTRO-PLATING ARRANGEMENTS IN PARTICULAR. 

The actual electro-plating plant consists of the following parts : 
1. The sources of current (batteries or dynamo-electric machines) 
'with auxiliary apparatus. 2. The current conductors. 3. The 
baths consisting of the vats, the galvanic solution, the anodes and 
the conducting rods with their binding screws. 4. The apparatuses 
for cleansing, rinsing, and drying. The sources of current have 
already been discussed in Chap. III. p. 44, and the laws govern- 
ing the suitable coupling of the elements on p. 31. 

A. Arrangement with elements. — In working with elements it 
is first necessary to have a clear idea of the size of the area 
of the articles which are to be at one time electro-plated in a bath, 
and of the magnitude of the resistance opposed by the bath to 
the current. This and the size of the anodes show how many 
elements must be put together for a battery, and how the elements 
are to be coupled. Suppose we have a nickel bath which requires 
for its decomposition a current of 2.5 volts of electro-motive force 
or tension ; now since, according to p. 50, a Bunsen element yields 
a current of 1.88 volts, the reduction of the nickel cannot be 
effected with one such element, but two elements must be coupled 
for tension one after the other, whereby, leaving the conducting 
resistance of the wires out of consideration, a tension of 2 x 1.88 = 
3.76 volts is obtained with which the decomposition of the solution 
can be effected. If, on the other hand, we have a silver bath 
, which requires only J volt for its decomposition, we do not couple 
two elements one after the other, because the electro-motive force 
of a single element suffices for the separation of the silver. On 
p. 32, it has been seen that by coupling the elements one after the 
other (coupling for tension) the electro-motive force of the battery 
is increased, but the quantity of current is not increased, and that 
to attain the latter the elements must be coupled alongside of one 



80 



ELECTRO-DEPOSITION OF METALS. 



another (coupled for quantity). Hence in a group of, for instance, 
three elements coupled one after another, only one single zinc 
surface of the elements can be considered effective in regard to 
the quantity of current. Now the larger the area of articles at 
the same time suspended in the bath is, the greater the number of 
such effective zinc surfaces of the group of elements to be brought 
into action must be, and if for baths with medium resistance it 
may be laid down as a rule that the effective zinc surface must 
be at least as large as the area of the articles, provided the surface 
of the anodes is at least equal to the latter, the approximate num- 
ber of elements and their coupling for a bath can be readily found. 
Let us take the nickel bath, which, as above mentioned, requires 
a current of 2.5 volts, and for the decomposition of which two 
elements must, therefore, be coupled one after the other, and sup- 
pose that the zinc-surface of the Bunsen elements is 500 square 
centimetres, then the effective zinc-surface of the two elements 
coupled one after the other will also be 500 square centimetres ; 
hence a brass sheet 20 X 25=500 centimetres can be conveniently 
nickeled on one side with these two elements, or a sheet 10 x 25= 
250 centimetres on both sides. Now suppose the surface to be 
nickeled were twice as large, then the two elements would not 

Fig. 32. 




suffice, and a second group of two elements, coupled one after the 
other, would have to be joined to the first group for quantity as 
shown in Fig. 3, or perspectively in Fig. 32. Three times the 
object-surface would require three groups of elements and so on. 

In giving these illustrations it is supposed the objects are to 
have a thick solid plating ; for rapid plating with a thin deposit 



ELECTRO-PLATING ESTABLISHMENTS. 81 

a different course has to be followed. Only a slight excess of 
electro-motive force in proportion to the resistance of the bath 
being in the above-mentioned case present, reduction takes place 
slowly and uniformly without violent evolution of gas on the 
objects, and by the process thus conducted the deposit formed is 
sure to be homogeneous and dense, since it absorbs but slight 
quantities of hydrogen, and in most cases it can be obtained of 
sufficient thickness to be thoroughly resistant. If, however, the 
operation is to be executed quickly and without regard to great 
solidity and thickness of the deposit, the elements have to be 
coupled so that the electro-motive force is sufficiently large for 
the current to readily overcome the resistance of the bath. This 
is attained by coupling three, four, or more elements one after the 
other, as shown in the scheme, Fig. 1. However, such deposits 
can never be homogeneous because they condense and retain rela- 
tively large quantities of hydrogen. 

As regards the filling and other management of the batteries, 
the reader is referred to p. 51, under Bunsen elements. Having 
seen how many elements are required, and how they have to be 
coupled to form a battery for certain purposes, we will next con- 
sider the auxiliary apparatuses. 

Only in very rare cases will it be possible to always charge a 
bath or several baths with the same object-area ; and according 
to the amount of business, or the preparation of the objects by 
grinding, polishing and pickling, at one time large and at another 
small areas will be suspended in the bath. Now, suppose a 
battery suitable for a correct deposit upon an area of, say five 
square feet, has been grouped together ; and, after emptying the 
bath, a charge only half as large is introduced, the current of the 
batteiy w T ill, of course be too strong for this reduced area, and 
there will be danger of the deposit not being homogeneous and 
dense, but forming with a crystalline structure, the consequence of 
which, in most cases, will be slight adhesiveness, if not absolute 
uselessness. With sufficient attention the total spoiling of the 
articles might be prevented by removing the objects more quickly 
from the bath. But this is groping in the dark, the objects being 
either taken too soon from the bath, when not sufficiently plated, 
6 



82 



ELECTRO-DEPOSITION OF METALS. 



or too late, when the deposit already shows the consequences of 
too strong a current. 

To control the current an instrument called the current-regulator, 
resistance board, or switch board has been constructed, which allows 
of the current-strength of a battery being reduced without the 
necessity of uncoupling elements. It is evident that the current of 
a battery, if too strong, can be weakened by decreasing the number 
of elements forming the battery, and also by decreasing the surface 
of the anodes, because the external resistance is thereby increased. 
This coupling and uncoupling of elements is, however, not only a 
time-consuming, but also a disagreeable labor ; and it is best to use 
a resistance board, with which by the turn of a handle, the desired 
end is attained. Figs. 33 and 34 show this instrument. Its action 
is based upon the following conditions : As explained on p. 33, the 
maximum performance of a battery takes place when the external 
resistance is equal to the internal resistance of the battery. By 
increasing the external resistance, the performance is decreased, 
and a current of less intensity will pass into the bath when re- 
sistances are placed in the circuit. The longer and thinner the 



Fig. 33. 




Fig. 34. 



■onn^rjiL jn 



TotheBqtfi, 




To the Bath 



conducting wire is, and the less conducting power it possesses, the 
greater will be the resistance which it opposes to the current. 
Hence, the resistance board consists of metallic spirals which 
lengthen the circuit, contract it by a smaller cross-section, and by 



ELECTRO-PLATING ESTABLISHMENTS. 83 

the nature of the metallic wire have a resistance producing effect. 
For a slight reduction of the current, copper spirals of various 
cross-sections are taken, which are succeeded by brass spirals, and 
finally by German silver spirals, whose resistance is eleven times 
greater than that of copper spirals of the same length and cross- 
section. In Fig. 33 the conducting wire coming from the battery 
goes to the screw on the left side of the resistance board, which is 
connected by stout copper wire, with the first contact-button on 
the left ; hence by placing the metallic handle upon the button 
furthest to the left, the current passes the handle without being 
reduced, and flows off through the conducting wire secured in the 
setting-screw of the handle. By placing the handle upon the 
next contact-button, to the right, two copper spirals are brought 
into the circuit ; by turning the handle to the next button four 
spirals are brought into the circuit, and so on. By a choice of 
the cross-sections of the spirals, their length and the metal of 
which they are made, the current may be more or less reduced as 
desired. 

To control the reduction of the current effected by the resistance, 
a galvanometer is placed behind it. It consists of a magnetic 
needle oscillating upon a pin, below which the current is con- 
ducted through a strip of copper, or, with weaker currents through 
several coils of wire. The electric current deflects the magnetic 
needle from its position and the more so the stronger the current 
is ; hence the current-strength of the battery can be determined 
by the greater or smaller deflection. 

For a weak current, such as, for instance, that yielded by two 
elements, it is of advantage to use a horizontal galvanometer (Fig. 
35). It is screwed to a table by means of 
a few brass screws in such a position that Fi g- 35 - 

the needle in the north position, which it 
occupies, points to 0° when no current 
passes through the instrument. Articles 
of iron and steel must, of course, be kept 
away from the instrument. For stronger 

currents, it is better to combine a vertical galvanometer with the 
resistance board and fasten it to the same frame as shown in Fig. 
33. The screw of the handle of the resistance board is connected 




84 



ELECTRO-DEPOSITION OF METALS. 



with one end of the copper strip of the vertical galvanometer 
while the other is connected with the screw on the right side of 
the resistance board in which is secured the wire leading to the 
bath. The resistance board and galvanometer are placed in one 
conducting wire only, either in that of the anodes or of the objects ; 
one of these wires is simply cut and the end connected to the 
battery is secured in the setting screw on the side of the resistance 
board marked " strong," while the other end which is in connec- 
tion with the bath is secured in the setting screw on the opposite 
side marked " weak." The entire arrangement will be perfectly 
understood from Figs. 36 and 37. 



Fig. 36. 




OCZ □&- 



Having discussed the advantages derived from the use of the 
resistance board, it remains to add a few words regarding the 
indications made by the galvanometer. Since the greater deflec- 
tion of the needle depends, on the one hand, on the greater current- 
strength, and, on the other, on the slighter resistance of the outer 
closing arc (conducting wires, baths and anodes), it is evident that 
a bath with slighter resistance, when worked with the same battery 
and containing the same area of anodes and objects, will cause the 
needle to deflect more than a bath of greater resistance under other- 
wise equal conditions. Hence the deductions drawn from the 



ELECTRO-PLATING ESTABLISHMENTS. 



85 



position of the needle for the galvanic process are valid only for 
determined baths and determined equal conditions, but with due 
consideration of these conditions are of great value. Suppose a 
nickel bath always works with the same area of objects and of 



Fitf. 37. 




anodes, and experiments have shown that the suitable current- 
strength for nickeling this area of objects is that at which the 
needle stands at 15° ; and suppose further that the battery has 
been freshly filled and causes the needle to deflect to 25°, then 
the handle of the resistance board will have to be turned so far to 
the right that the needle, in consequence of the introduced resis- 
tances, returns to 15°. Now, if after w T orking for some time, the 
battery yields a weaker current the needle, since the resistance 
remains the same, will constantly retrograde and has to be brought 
back to 15° by turning the handle to the left, when a current of 
equal strength of the former will again flow into the bath. This 
play is repeated until finally the handle stands upon the button 
furthest to the left, at which position the current flows directly 
into the bath without being influenced by the resistances of the 
resistance board. If now the needle retrogrades below 15°, it is 
an indication to the operator that he must renew the filling of the 
battery if he does not prefer suspending fewer objects in the bath. 
For this reduced object-area it is no longer required for the 



86 ELECTRO-DEPOSITION OF METALS. 

needle to stand at 15° in order to warrant a correct progress of 
the galvanic process, since the resistance being, in this case greater, 
a deflection to 10° or still less may suffice. This illustration will 
sufficiently show that the current-indication by the galvanometer 
is not and cannot be absolute, but that the deductions must always 
be drawn with due consideration to the conditions — area of objects 
and of anodes, distance between them. An operator to be sure 
in this respect, and before all, wishing to work scientifically, will 
replace the galvanometer by a volt-meter which indicates the abso- 
lute magnitude of the tension passing into the bath, as will be 
explained later on. 

It frequently happens that in consequence of defective contacts 
with the binding screws of the battery or by the conductors of the 
objects and of the anodes touching one another (short circuit with 
non-insulated conducting wires) no current whatever flows into 
the bath. Such an occurrence is immediately indicated by the 
galvanometer, the needle being not at all deflected in the first 
case, while in the latter the deflection will be entirely different 
from the usual one. The magnetic needle of the galvanometer 
also furnishes a means of recognizing the polarity of the current. 
If the galvanometer be placed in the positive conductor by secur- 
ing the wire coming from the battery in the binding screw on the 
south pole of the galvanometer and the wire leading to the bath 
in the binding screw on the north pole of the needle, the needle, 
according to Ampere's law, will be deflected in the direction of 
the hands of a watch, i. e., to the right if the observer stands so 
in front of the galvanometer as to look from the south pole 
towards the north pole, because the battery-current flows out from 
the positive pole through the conducting wire, anodes and fluid 
to the objects and from these back through the object wire to the 
negative pole of the battery. If now in consequence of the 
counter-current formed in the bath by the metallic surfaces of 
dissimilar nature (see later on), and flowing in an opposite direc- 
tion to that of the battery-current, the latter is weakened, the 
needle will constantly further retrograde from the zero point, and 
when the counter or polarizing current becomes stronger than the 
battery-current, it will be deflected in an opposite direction as 
before. Hence, by observing the galvanometer the operator can 



ELECTRO-PLATING ESTABLISHMENTS. 87 

avoid the annoyiDg consequences of polarization which will be 
further discussed under nickeling. 

From what has been said in this chapter and in the theoretical 
part it is self-evident what rules have to be observed in conduct- 
ing the current. Since the current-strength is weakened by 
resistance, the cross-section of the current-carrying wire as well 
as of that leading to the objects and to the anodes must be of a 
size corresponding to the current-strength, and the material for 
the wires should possess as high a conducting power as possible. 
Chemically pure copper is best suited for this purpose. Some 
information for calculating the thickness of the wires will be 
found at the end of the section "arrangement with dynamo 
machines." 

The positive or anode wire effects the connection between the 
anodes of the bath and the positive pole (anode or carbon pole) 
of the battery, while the negative or object wire brings the objects 
in the bath into metallic contact with the negative (zinc) pole of 
the battery. As previously mentioned the resistance board with 
galvanometer is placed in one or the other of the wires. 

For conducting the current it is best to use insulated copper 
wires; bright wires, if used, must be insulated one from another 
as well as from damp walls by pieces of wood or porcelain, as 
otherwise there will be a loss of current. 

Vats for baths. — The choice of material for the vats depends 
on the nature and properties of the galvanic solutions. Solu- 
tions containing potassium cyanide require vats of stoneware or 
enamelled cast-iron ; nickel baths as well as other baths which do 
not attack pitch and rosin, may be kept in pitched wooden vats. 
For small baths up to 300 quarts, a vat of stoneware or enamelled 
cast-iron is most advantageous. Wooden vats must be carefully 
constructed, and are best secured at the ends by bolts and nuts as 
shown in Fig. 38, which serve to hold the sides firmly against 
the end pieces. The vat is then coated with a mixture of equal 
parts of pitch and rosin boiled with a small quantity of linseed 
oil. Another mixture which has been found to afford a good 
protective covering to wood consists of 10 parts of gutta percha, 
3 of pitch, and 1J each of stearin and linseed oil, melted together 
and incorporated. 



88 ELECTRO-DEPOSITION OF METALS. 

For large baths containing potassium cyanide, holders of bricks 
laid in cement, and inside plastered with cement may also be used, 
or holders of boiler plate lined inside with a layer of cement. 

Fig. 38. 




The vats for heating baths are best made of enamelled iron or 
wood lined with sheet-lead ; stoneware vats do not bear heating. 

It is advantageous to provide the narrow sides of the vats with 
semi-circular notches for the conducting rods to rest in to prevent 
their rolling away. When using stoneware vats the conducting 
rods are laid directly upon the vats ; vats of other material must 
be provided with an insulated rim of wood or the rods are insu- 
lated by pushing a piece of rubber hose over their ends. Accord- 
ing to the size of the bath, 3, 5, 7, or more conducting rods, best 
of pure massive copper, are used. 

To secure the uniform coating of the objects with metal they 
must be surrounded as much as possible by anodes, i. e., the posi- 
tive pole plates of the metal which is to be deposited. For fiat 
objects it suffices to suspend them between two parallel rows of 
anodes, the most common arrangement being to place three rods 
across the bath, the two outermost of which carry the anodes, 
while the objects are secured to the centre rod. For wide baths 
five conducting rods are frequently used, but they should always 
be so arranged that a row of objects is between two rows of 
anodes. The arrangement frequently seen with four rods across 
the baths, of which the outermost carry anodes, and the other 



ELECTRO-PLATING ESTABLISHMENTS. 



89 



two objects, is irrational if the objects are to be uniformly plated 
on all sides, because the sides turned towards the anodes are 
coated more strongly than those suspended opposite to the other 
row of objects. 

For large round objects it is better to entirely surround them 
with anodes, if it is not preferred to turn them frequently, so that 
all sides and portions gradually feel the effect of the immediate 
neighborhood of the anodes. (See Nickeling.) 

For objects to be plated on one side only the centre rod may be 
used for the anodes, and the two outer ones for the objects ; the 
surface to be plated being, of course, turned towards the anodes. 

The rods carrying the anodes, as well as those carrying the 
objects, must be well connected with each other, which is effected 



Fie. 39. 



Fig. 40. 



Fig. 41. 






Fie. 42. 



by means of binding screws of the forms shown in Figs. 39, 40, 
and 41. 

The anodes are suspended from the cross rods by strong hooks 
of the same metal, so that they can be entirely immersed in the 
bath (Fig. 42) ; hooks of another soluble 
metal would contaminate the bath by dis- 
solving in it, and this must be strictly 
avoided as it would cause all sorts of dis- 
turbances in the correct working of the 
bath. In case hooks of another metal, 
except platinum, are used, the anodes 
must be hung so that they project above 
the surface of the liquid, and the hooks 
not being immersed are, therefore, not 
liable to corrosion ; but the anodes are 




90 ELECTRO-DEPOSITION OF METALS. 

then not completely used up, the portion dipping into the solution 
being gradually dissolved, whilst the portion projecting above the 
fluid remains intact. Instead of wire hooks, strips of sheet of the 
same metal as the anodes, and fastened to them by a rivet may 
also be used (Fig. 43). For suspending the objects soft pure 
copper wire of a thickness corresponding to the size and weight 
of the objects is preferably employed. 

To keep the rods clean and to protect them from the fluid drain- 
ing off from the articles when taken from the bath, it is advisable 
to cover them with a roof of strips of wood ( A), or a semicircular 
strip of zinc coated with ebonite lacquer; by this means the 
frequent scouring of the rods, which otherwise is necessary in 
order to secure a good contact with the hooks of the anodes, is 
done away with. 

The galvanic solutions, briefly called baths, will be especially 
discussed in speaking of the various electro-plating processes. It 
still remains to consider the cleansing and rinsing apparatuses. 
Every electro-plating establishment, no matter how small, requires 
at least one tub or vat in w T hich the objects can be rubbed or 
brushed with a suitable agent in order to free them from grease. 
This is generally done by placiug a small kettle or stoneware pot 
containing the cleansing material at the right hand side of the 
operator alongside the vat or tub. Across the latter, which is half 
filled with water, is laid a board of soft wood covered with cloth, 
which serves as a rest for the objects previously tied to wires. 
The objects are then scrubbed with a brush or rubbed with a 
piece of cloth dipped in the cleansing agent. The latter is then 
removed by rinsing the objects in the water in the tub and draw- 
ing them through water in another tub. By this cleansing pro- 
cess a thin film of oxide is formed upon the metals, which would 
be an impediment to the intimate union of the electro-deposit 
with the basis-metal. This film of oxide has to be removed by 
dipping or pickling, for which purpose another vat or tub con- 
taining the pickle, the composition of which varies according to 
the nature of the metal, has to be provided. After dipping, the 
objects have to be again thoroughly rinsed in water to free them 
from adhering pickle, so that for the preparatory cleansing pro- 
cesses three vessels with water, which has to be frequently renewed, 



ELECTRO-PLATING ESTABLISHMENTS. 91 

as well as the necessary pots for the pickling solutions have to be 
provided. In case the vat for cleansing the articles or the box- 
like table (see Fig. 49) is provided with a rose-jet, under which 
the objects are rinsed, the other vats are not required. 

After having received the electro-deposit the objects have to 
be again rinsed in cold water, which can be done in one of the 
three vats or with the rose-jet, and finally have to be immersed in 
hot water until they have acquired the temperature of the latter. 
How the water is heated makes no difference, and depends on the 
size of the establishment. The heated objects are then immediately 
dried in a box filled with dry, fine saw-dust — that of maple, poplar, 
or other wood free from tannin being suitable for the purpose. 

B. Arrangements with dynamo-electric machines. — For setting up 
and running the machines the following rules are to be observed. 
Larger machines are to be screwed to square wooden joists resting 
upon a solid brick foundation about six inches above the floor ; 
smaller machines may be placed upon and fastened to strong 
tables secured to the floor or wall. The principal point is that the 
foundation or table is not subjected to shocks which would be 
transferred to the machines and cause, by the vibration of the 
brushes, a larger formation of sparks, and consequent greater wear 
of certain portions of the machine. Foundations about 8 inches 
wider on each side than the machine and built of brick and 
cement have been found most suitable. If possible the machines 
should be located in the neighborhood of the baths they are to 
feed, since the greater the distance from the bath at which they 
are placed, the larger the cross-section of the principal conducting 
wire must be, and the more troublesome the regulation of the 
current will prove, provided it is not intended to place another 
resistance board just in front of the bath, which is the best plan 
for regulating the current with the greatest nicety. 

It is best to set the dynamo in motion by means of a gearing 
with loose and fast pulley so as to render a gentle engaging of 
the machine possible, and not directly from the fly-wheel of the 
motor, whereby in consequence of the jumping and dragging of 
the belt it is apt to run less regularly. The bearings should be 
kept well lubricated, best with automatic oilers filled with good 
lubricating oil. The stated number of revolutions per minute 



92 ELECTRO-DEPOSITION OF METALS. 

should not be exceeded, since by the stronger current thereby 
generated the machine might become very hot and suffer injury. 
On the other hand, when a weaker current is required, the machine 
may be run more slowly than the maximum performance with the 
prescribed number of revolutions. The brushes which conduct 
the current from the commutator should be firmlv secured in their 
holders by means of screws, and the levers pressing them by 
means of spiral springs against the commutators must be fixed 
so that the brushes securely and uniformly slide upon them; 
pressing the brushes too tightly against the commutators should, 
however, be avoided. While the machine is running the brushes 
should not be lifted off, since the large sparks thereby produced 
strongly attack the brushes and the commutator, and this favorite 
amusement of the workmen should be strictly forbidden. 

When the machine is for the first time set in motion, the com- 
mutator should be gone over with a smooth file or emery paper 
to remove any projections of the insulation between the metallic 
plates, which readily swell when the machine stands in a damp 
place. The commutator should also daily be freed, by wiping, 
from copper-dust, and if after some time it wears unevenly be 
made smooth with a file. 

The inductor-ring should at least once every week be cleansed 
from copper-dust by means of a small bellows or other instru- 
ment. Movable articles of iron and steel should be kept away 
from the machine when running, as they might be attracted by 
the portions of the machine which have become strongly magnetic. 

The object- and anode- wires must be insulated from each other, 
as well as from the ground and damp brick-work by dry wood 
or porcelain, and the places of junction kept bright. 

The employment of special wire carriers of the form shown in 
Fig. 44, is advisable. They consist of cast-iron arms, provided 

_. .. on the ends with a case between the lower 

Fig. 44. 

and upper cover of which are disks of hard 
rubber. 

To regulate the current resistance boards 
or current-regulators are used. They are 
constructed according to the same principle 
as those described under " Arrangement with 




ELECTRO-PLATING ESTABLISHMENTS. 93 

Elements" (p. 82), only the spirals are longer and of a larger 
cross-section, and the entire instrument is stronger. Instead of 
upon wood the contact buttons are mounted upon slate plates, as 
wood would be carbonized by the spirals becoming hot. 

In case one machine has to feed several baths of dissimilar 
nature and composition, the regulation of the current for all the 
baths in the main conducting wire is not feasible on account of 
the different resistances ; and it will be necessary to place a resist- 
ance board in front of every bath. With dynamos of the Schuc- 
kert and Lahmeyer type, which are very practical, it will be 
further necessary to place a resistance board (the resistance board 
of the dynamo) in the windings of the machine, in order to be 
enabled to generate more or less current, as may be required, and 
to avoid an unnecessary consumption of power. From the scheme 
(Fig. 45), for such a machine with its auxiliary apparatus, the 
main conducting wire and a few baths, the reader will readily see 
what is required. 

The dynamo resistance board will have to be placed so that the 
machine yields somewhat more current than with due considera- 
tion to the object-area is required for all the baths, while the 
supply of current for each bath is regulated by the resistance 
board placed in front of it. In the scheme (Fig. 45), are sketched 
two further instruments for measuring the quantity and the elec- 
tromotive force of the current ; by the first, called the ampere- 
meter, or better, ammetre, the whole current-strength can be 
directly read off in amperes ; and by the other, called the volt- 
meter, the electro-motive force or tension in volts. The ampere- 
meter is placed in one conducting wire only, either in that of the 
object or of the anodes, while the voltmeter is connected with 
both, one setting screw being joined, on the points where the ten- 
sion is to be measured, to the object-wire by a 0.039 inch thick 
copper wire, and the other to the anode-wire. In the sketch 
(Fig. 45), the voltmeter being directly in contact with the poles 
of the machine will indicate the tension produced by it. This 
mode of placing the measuring instruments is, however, not suit- 
able for establishments using baths of different compositions and 
different resistances ; in such case the tension must be measured on 
the bath itself, and consequently the voltmeter has to be placed in 



94 



ELECTRO-DEPOSITION OF METALS. 




I + 



the conducting wire between the resistance board of each bath 
and the bath itself. However, for a large establishment, using 
many baths, it would be quite an item of expense to provide each 



ELECTRO-PLATING ESTABLISHMENTS. 



95 



bath with a special voltmeter. But this is not necessary, one 
voltmeter sufficing for three, four, or even more, baths. In order 
conveniently to read off on the voltmeter the tension of the cur- 
rent passing into one of these baths, a shunt is required, the con- 
struction of which is seen from Figs. 46 and 47. 

Fig. 46 shows the coupling of the main object-wire ( — ), and 

Fig. 46. 




the main anode-wire ( + ), with the resistance boards R x and i? 2 , 
the voltmeter V, the shunt Z7, and the two baths. 



9 b ELECTEO-DEPOSITION OF METALS. 

In Fig. 47 the coupling is enlarged, and upon this the follow- 
ing description is based : Suppose the main object-wire and 
anode-wire to be connected with the corresponding poles of a 

Fig. 47 




dynamo-machine or a battery, which for the sake of a clearer 
view is omitted in the illustration. The shunt U consists of a 
brass handle, mounted with a brass foot, upon a board ; in the 
foot is a screw, with which is connected by a 0.039 inch thick 
copper wire, one of the pole-screws of the voltmeter. The brass 
handle drags with spring pressure upon contact buttons connected 
by copper wire with the setting screws 1, 2, 3, 4, 5 (upon the 
shunt board), which serve for the reception of the 0.039 inch 
thick insulated wires, 1, 2, 3, 4, for measuring the tension, which 
branch off from the various baths or resistance boards. The 
other pole-screw of the voltmeter is directly connected with the 
main anode-wire. From the main object- wire, a wire whose cross- 
section depends on the strength of the working current, passes 
to the screw, marked " strong," of the resistance board R t ; the 
screw marked " weak," of the resistance board R v is connected 
by a correspondingly stout wire with the object-wire of bath I, 
and at the same time with the binding-screw 1 of the shunt. 
The resistance board M 2 , of the bath II, is in the same manner 



ELECTRO-PLATING ESTABLISHMENTS. 97 

connected with the main object-wire, the bath and the binding- 
screw 2 of the shunt ; also the resistance boards i2 3 and R 4 of the 
baths III and IV, which are not shown in the illustration. With 
the main anode-wire each bath is directly connected by leading 
the current to an anode-rod of the bath by means of binding 
screws and a stout copper wire, and establishing a metallic con- 
nection between this anode-rod and the next one. However, in- 
stead of connecting both, the current may also be led from the 
main anode-wire to each anode-rod. 

In the illustration, the handle of the shunt rests upon the 
second contact-button to the left, which is connected with the 
binding-screw 2 of the board. In the latter is secured the wire 
for measuring the tension of the resistance board R 2 ; and hence 
the voltmeter V will indicate the tension of the current in bath II. 
Suppose bath II is full of objects, and with the position of the 
handle of the resistance board, at " weak," as shown in the illus- 
tration, the voltmeter indicates 1.5 volts, while the most suitable 
tension for the bath is 2.5 volts, the handle of the resistance board 
is turned to the left until the needle of the voltmeter indicates the 
desired 2.5 volts. 

By turning the handle of the shunt Z7to the left, so that it 
rests upon the contact-button 1, the measuring wire of bath II is 
thrown out, and the voltmeter indicates the tension in bath I. If 
the handle rests upon contact-button 3, the tension in bath III is 
indicated, and so on. 

In working the different baths in a larger establishment, each 
bath is best directly fed from the main conducting wire after the 
current has been brought to the proper strength by the resistance 
board. Coupling the baths one after another so that the current 
passes from one bath to the other is only practicable for metallurgi- 
cal processes — gaining of metals — where every bath contains the 
same area of objects and anodes, has the same resistance, and 
works under the same conditions. 

Fig. 48 shows the ground plan of an electro-plating establish- 
ment. NN t is a dynamo-electric machine, with 300 amperes, at 
4 volts' tension. The resistance board belonging to the machine, 
and placed in the conductor, is indicated by No. 1, and is screwed 
to the wall. The main conductors marked — and -f , run along 
7 



ELECTRO-DEPOSITION OF METALS. 



;///// 1 1 n / / j //////// //jjjjjn/ /, ZZZZ1 //////// Z2 I 







the wall, from which they are separated by wood, and consist of 
rods of pure copper 0.59 inch in diameter. The rods are con- 
nected with each other by brass-coupling boxes with screws. 



ELECTKO-PEATING ESTABLISHMENTS. 99 

From the negative pole and the positive pole of the machine to 
the object-wire and anode-wire lead two wires, each 0.27 inch in 
diameter, one end of each is bent to a flat loop and secured under 
the pole screws of the machine, while the other ends are screwed 
into the second bore of the binding screws screwed upon each con- 
ductor. To the right and left of the machine the baths are placed ; 
Zn, indicating zinc bath ; Ni Ni, nickel baths ; Ku, copper cyan- 
ide bath ; 3Ig, brass bath ; S K, acid copper bath ; Si, silver bath ; 
and Go, gold bath. Each of the first-named five baths has its 
own resistance board designated by 2, 3, 4, 5, 6. However, be- 
fore reaching the acid copper bath, and the silver and gold baths, 
the current is conducted through two resistance boards, 7 and 8. 
Since these baths only require a current of slight electro-motive 
force, it is necessary to place two, and in many cases, even three 
or four resistance boards, one after another, unless it be preferred 
to feed these baths with a special machine of less tension. 

From Fig. 48 it will be seen that the current weakened by the 
resistance boards 7 and 8 serves for conjointly feeding the acid- 
copper, silver and gold baths. Hence, practically, only one bath 
can be allowed to work at one time, as otherwise each bath would 
have to be provided with as many resistance boards as would be 
required for the reduction of the tension. For want of space the 
gold bath is placed in the sketch behind the silver bath ; but 
as their resistance is not the same, they must also be placed 
parallel. 

The coupling of the voltmeter and shunt is omitted in the illus- 
tration. Their arrangement will be understood from Fig. 46. 

L is the lye-kettle ; it serves for cleansing the objects by means 
of hot caustic potash or soda lye from grinding and polishing dirt 
and oil. Instead of the preparatory cleansing with hot lye, which 
saponifies the oils, the objects may be brushed off with benzine, 
oil of turpentine or petroleum, the principal thing being the re- 
moval of the greater portion of the grease and dirt, so that the final 
cleansing, which is effected with lime paste, does not require too 
much time and labor. It is also advisable to cleanse the objects, 
in one way or the other, immediately after grinding, as the dirt, 
which forms a sort of solid crust with the oil, is difficult to soften 



100 



ELECTKO-DEPOSITION OF METALS. 



and to remove when once hard. The table for freeing the articles 
from grease stands alongside the lye-kettle, and is shown in per- 
spective, in Fig. 49. It consists of a box with legs, which by 
four partitions is divided into two large divisions, A and B, and 
three smaller ones, C, D and E. The separate divisions are lined 




with sheet lead. Across the divisions A and B boards covered 
with cloth are laid, upon which the articles are brushed for the 
final cleaning with lime paste. Over each of these divisions is a 
rose-jet, provided with a cock, under which the articles are rinsed 
with water. The discharge pipes from A and B are provided 
with valves, and are tightly soldered into the bottom of the box. 
Of the smaller partitions, D serves for the reception of the lime 
paste, while C and E each contain two pots or small stoneware 
vats with pickling fluid. In Fig. 48 these vats are indicated by 
11 and 12. The two marked 11 contain dilute sulphuric acid for 
pickling iron and steel articles, while those marked 12 contain 
dilute potassium cyanide solution for pickling copper and its 
alloys, and Britannia, etc. For cleansing smaller articles, four men 
can at one time work on such a table ; but for cleansing larger 
articles only two. The advantage of such a box-table is, that 
everything is handy together, and that the pickle, in case a pot 
should break, cannot run over the floor of the workshop ; and that 
the latter is not spoiled by pickle dropping from the objects. The 



ELECTKO-PLATING ESTABLISHMENTS. 101 

small box K, on the side of the table, serves for the reception of 
the various scratch-brushes. 

Between the lye-kettle L and the box-table, in Fig. 48, is a 
frame (14) for the reception of brass and copper wire hooks of 
various sizes and shapes suitable for suspending the objects in the 
bath. 

The reservoir W, filled with water, standing in front of the 
machine, serves for the reception of the cleansed and pickled ob- 
jects, if for some reason or another they cannot be immediately 
brought into the bath. 

H W is the hot water reservoir in which the plated objects are 
heated to the temperature of the hot water, so that they may 
quickly dry in the subsequent rubbing in the sawdust box Sp. 
Before polishing the deposits, iron and steel objects are finally 
thoroughly dried in the drying chamber T (Fig. 48), heated 
either by steam or direct fire. By finally adding to the appliances 
a large table, 13, for sorting and tying the objects on the copper 
wires, and a few shelves not shown in the illustration, everything 
necessary for operating without disturbance will have been pro- 
vided. 

What has been said in the preceding section in regard to the 
conducting wires, vats, conducting rods, anodes, etc., also applies 
to establishments using electro-dynamo machines. 

In calculating the thickness of the conducting wires for dyna- 
mos, 1 square millimetre (0.001 square inch) of conducting cross- 
section is to be allowed for every 3 amperes for so-called short 
circuits up to 20 metres (21.87 yards). This is valid for currents 
up to 500 amperes ; for longer circuits 1 J to 2 amperes are calcu- 
lated for the square millimetre of conducting cross-section. 



102 ELECTRO-DEPOSITION OF METALS. 



CHAPTEK V. 

TREATMENT OF THE METALLIC ARTICLES. 

The objects having to undergo both a mechanical and chemical 
preparation, each of them will be considered separately. 

A. Mechanical Treatment. 

1. Before electro-plating. — If the objects are not to be electro- 
plated while in a crude state, which is but rarely feasible, the 
mechanical treatment consists in imparting to them a cleaner sur- 
face by scratch-brushing, or a smoother and more lustrous one, by 
grinding and polishing. It may here be explicitly stated that 
scratch -brushing of electro-plated objects is not to be considered 
a part of their preparation, since such scratch-brushing is executed 
in the midst of, or after the electro-plating process, its object being 
to effect a change of the galvanic deposition in more than one 
direction, and not the cleansing of the surface of the metallic 
base. The following directions, therefore, apply only to the 
scratch-brushing of objects not electro-plated. The scratch-brush- 
ing of galvanic depositions will be considered later on. In regard 
to grinding we have to deal with the subject only in so far as it 
relates to smoothing rough surfaces by the use of grinding pow- 
ders possessing greater hardness than the metal to be ground ; 
with grinding in the sense of instrument grinding, the primary 
object of which is to provide the instrument with a cutting edge, 
we have nothing to do. 

Scratch-brushing may be effected either by hand or by a scratch- 
brush lathe. In the first place scratch-brushes of more or less 
hard brass or steel wire, according to the hardness of the metal to 
be manipulated are used. Various forms of brushes are employed, 
the most common ones being shown in the accompanying illustra- 
tions, Figs. 50 to 56. 

In scratch-brushing it is recommended to remove, or at least to 



TREATMENT OF METALLIC ARTICLES. 



103 



soften, the uppermost hard and dirty crust (the scale) by immersing 
the objects in a pickle, the nature of which depends on the variety 



Fig. 50. 



Fig. 51. 



Fig. 52. 



Fig. 53. 




<<® 




Fig. 54. 



Fig. 55. 



Fig. 56. 





of metal, so that a complete removal of all impurities 
and non-metallic substances may be effected by means 
of the scratch-brush in conjunction with sand, pumice 
stone, powder or emery. The work is complete only 
when the article shows a clean metallic surface, other- 
wise the brushing (scouring) must be continued. Scratch- 
brushes must be carefully handled and looked after, and 
their wires kept in good order. When they become bent 
they have to be straightened, which is most readily effected by 
several times drawing the brush, held in a slanting position, over 
a sharp grater such as is used in the kitchen. By this means the 
wires become disentangled and straightened out. 



104 



ELECTKO-DEPOSITION OF METALS. 



Hand scratch-brushing being slow and tedious work large 
establishments use circular scratch-brushes which are attached to 
the spindle of a lathe. These circular brushes consist of round 
wooden cases in which, according to requirement, 1 to 6 or more 
rows of wire bundles, see Fig. 57, are inserted. 

Fig. 57. 




Brushes with wooden cases are, however, more suitable for 
scratch-brushing depositions than for cleansing the metallic base, 
since for the latter purpose a more energetic pressure is usually 
applied, in consequence of which the bundles bend and even 
break off, if the wire is anywise brittle. For cleansing purposes 
a circular scratch-brush, which the workman can readily refur- 
nish with new bundles of wire, deserves the preference. It is 
constructed as follows : A round iron disk about 0.11 inch thick, 
and from 5| to 7f inches in diameter, is provided in the centre 
with a hole so that it can be conveniently placed upon the spindle 
of the lathe. At a distance of from 0.19 to 0.31 inch from the 
periphery of the disk, holes 0.079 to 0.11 inch in diameter are 
drilled so that between each two holes is a distance of 0.15 inch. 
Draw through these holes bundles of wire about 3.93 inches long, 
so that they project an equal distance on both sides. Then bend 
the bundles towards the periphery, and on each side of the iron 
disk place a wooden disk 0.31 to 0.39 inch thick. The periphery 
of the wooden disk, on the side next to the iron disk, should be 
turned semi-annular, so that the wooden disks, when secured to 
the spindle press very lightly upon the wire bundles, and the latter 
remain very mobile. When a circular scratch-brush constructed 
in this manner and secured to the lathe is allowed to make from 
1800 to 2000 revolutions per minute, the bundles of wire, in con- 
sequence of the centrifugal force, stand very rigid, but being 



TKEATMENT OF METALLIC AETICLES. 105 

mobile will give way under too strong a pressure without break- 
ing off, and can thus be utilized to the utmost. When required, 
the iron disk can be refurnished with wires in less than half an 
hour. An error frequently committed is that the objects to be 
cleansed are pressed with too heavy a pressure against the wire 
brushes. This is entirely useless, since only the sharp points of 
the wires are effective, the lateral surfaces of the bundles remov- 
ing next to nothing from the articles. 

In large establishments engaged in electro-plating cast-iron 
without previous grinding, the use of the sand-blast in place of 
the circular wire brush has recently been introduced with great 
advantage. Objects with deep depressions, which cannot be 
reached with the scratch-brush, as well as small objects, which 
cannot be conveniently held in the hand and pressed against the 
revolving scratch-brush, can only be brought by the sand-blast 
into a state of sufficient metallic purity for the electro-plating 
process. However, while the revolving scratch-brushes impart 
to the objects a certain lustre, they acquire by the sand-blast a 
dead lustre, and, hence, the blast is also frequently used for the 
purpose of deadening lustrous surfaces to their entire extent, or 
of producing contrasts ; for instance, dead designs upon a lustrous 
ground, or vice versa. 

Fig. 58 shows such a sand-blast. The compressed air, whose 
pressure must be at least equal to an 18f-inch column of water, 
passes through the blast-pipe A into a nozzle running horizontally 
through the machine, and carries away from there a jet of sand 
which falls into the outflowing blast and is hurled upon the 
objects placed under the nozzle. The objects rest upon sheet- 
iron plates or in boxes of sheet-iron, which, moving at a slow 
rate, pass under the nozzle ; the motion is effected by the shafts 
B B, with the use of belts. To prevent dust the machine is 
encased in a wooden or sheet-iron case, a few windows allowing 
a view of the interior. The sand used in blasting collects in a 
box and is returned to the sand-reservoir by an elevator. 

The jet of sand acts not only upon the upper side of the 
objects, which it strikes first, but also almost as energetically 
upon the lower, so that, as a rule, the cleansing process is com- 



106 



ELECTRO-DEPOSITION OF METALS. 



pleted by one operation. Objects of a specially unfavorable shape 
must be passed twice or three times under the nozzle. 

Fig. 58. 




If a clean metallic surface is at one time to be given to a large 
number of small articles, such as buckles, steel beads, metal 
buttons, steel watch-chains, ferules, etc., a tumbling drum or box 
is frequently used. It generally consists of a cylindrical or 
polygonal box having a side door for the introduction of the 
work, together with sharp sand or emery, and is mounted hori- 
zontally on an axis furnished with a winch or pulley, so as to be 
revolved either by hand or power, as may be desired. In order 
to prevent certain objects, like hooks for ladies' dresses and the 
like, from catching each other and accumulating into a mass, a 
number of nails or wooden pegs are fixed in the interior of the 
drum. 

A very practical form of tumbling drum, in which a change 



TREATMENT OF METALLIC ARTICLES. 



107 



of position of the contents must constantly take place, is shown in 
Fig. 59. The drum A, of wood or iron, is obliquely placed upon 
the shaft B. The objects are introduced through the door C. 
The drum is revolved by a crank, or by a belt by means of the 




pulley D. All portions of the drum describe thereby ellipses, the 
walls of the drum being now raised (indicated by the dotted lines) 
and then lowered, so that the objects in the drum are in constant 
motion and rub against each other. By introducing together 
with the objects a suitable polishing powder with oil or water, 
such drums may be used not only for the preparatory cleansing 
of the objects, but also for polishing. 

Grinding. — For grinding the objects for the electro-plating 
process, wooden disks covered with leather coated with emery of 
various degrees of fineness are almost exclusively used. The 
wooden disks are made of thoroughly seasoned poplar in the 
manner shown in Fig. 60. The separate pieces are radially 
glued together, and upon each side in the 
centre a strengthening piece is glued and 
secured with screws so that each segment 
of the wooden disk is connected with the 
strengthening piece. The centre of the 
disk is then provided with a hole corre- 
sponding to the diameter of the spindle of 
the grinding lathe, to which it is secured 
by means of wedges. The periphery as 
well as the sides are then turned smooth. A good quality of 
leather previously soaked in water and cut into strips correspond- 
ing to the width of the wooden disk is then glued to the periphery 



Fte. 60. 




108 ELECTRO-DEPOSITION OF METALS. 

of the disk, and still further secured by pins of soft wood. When 
the glue is dry the disk is again wedged upon the spindle and the 
leather carefully turned ; it is then ready for coating with emery. 

For this purpose three different kinds of emery are used, a 
coarse quality (No. 60 to 80) for preparatory grinding, a finer 
quality (No. 00) for fine grinding, and the finest quality (No. 0000) 
for imparting lustre. The disks thus coated are termed respec- 
tively "roughing wheel," "medium wheel," and "fine wheel." 
With the first the surfaces of the objects are freed from the rough 
crust. The coarse-grained emery used for this purpose, however, 
leaves scratches, which have to be removed by grinding upon the 
medium wheel until the surface of the objects shows only the 
marks due to the finer quality of emery, which are in their turn 
removed by the fine wheel. 

In most cases brushing with a circular bristle brush may be 
substituted for the last grinding, the articles being moistened with 
a mixture of oil and emery No. 0000. Care must be had not to 
execute the brushing, nor the grinding with a finer quality of 
emery, in the same direction as the preceding grinding, but in a 
direction at a right angle to it. 

Treatment of the grinding disks. — The coating of the rough- 
ing wheels with emery is effected by applying to them a good 
quality of glue and rolling them in the dry coarse emery powder. 
For the medium and fine wheels, however, the emery is mixed with 
the glue and the mixture applied to the leather. When the first 
coat is dry, a second is applied, and finally a third. The whole 
is then thoroughly dried in a warm place. Before use, a piece of 
tallow is held to the revolving disk for the purpose of imparting 
a certain greasiness to it, and in order to remove any roughness 
due to an unequal application of the emery, it is smoothed by 
pressing a smooth stone against it. While the preparatory grind- 
ing upon the roughing wheel is executed dry, i. e. 9 without the use 
of oil or fat, in fine grinding the objects are frequently moistened 
with a mixture of oil or tallow and the corresponding No. of 
emery. When the layer of emery is used up, the remainder is 
soaked with warm water and scraped off with a dull knife. The 
leather of the disks on which oil or tallow has been used is then 



TREATMENT OF METALLIC ARTICLES. 



109 



thoroughly rubbed with caustic lime or Vienna lime* to remove 
the greasiness which would prevent the adherence of the layer of 
glue and emery to be applied later on. When the leather is 
thoroughly dry a fresh layer of emery may at once be applied. 

Grinding lathes. — For use, the grinding disks or buffs are 
wedged upon a conical cast-steel spindle provided with a pulley 
and working in hard wood bearings, as plainly shown in Fig. 61. 

Fig. 61. 




The cast iron standards are screwed to the floor; the wooden bear- 
ings can be shifted forward and backward by wedges and secured 
in a determined position by a set screw, thus facilitating the 
removal of the spindle after throwing off the belt. The disks 
being wedged upon a conical spindle they always run centrically, 
the changing of the disks requires but a few seconds and on account 
of the slight friction of the points of the spindle in the wooden 
bearings, the consumption of power is very slight. 

To avoid the necessity of throwing off the belt while changing 



* Vienna lime is prepared from a variety of dolomite which is first hurned 
then slacked and finally glowed for a few hours. It consists of lime and mag- 
nesia and should be kept in well-closed cans, as otherwise it absorbs carbonic 
acid and moisture from the air, and becomes useless. 



110 ELECTRO-DEPOSITION OF METALS. 

the grinding disks, double machines (Fig. 62), are used, the prin- 
ciple of conical spindles being, however, preserved. The shaft is 
provided with loose and fast pulley and coupling lever. 




Grinding is executed by pressing the surfaces to be ground 
against the face of the disk, moving the objects constantly to and 
fro. The operation requires a certain manual skill since, without 
good reason, no more should be ground away on one place than 
on another. Special care and skill are required for grinding large 
round surfaces. 

If the objects are not to be treated with the fine wheel, fine 
grinding is succeeded by brushing with oil and emery by means 
of circular brushes formed of bristles set in disks of wood (see 
Fig. 66). Genuine bristles being at present very expensive, vege- 
table fibre, so-called fibres, have been successfully substituted for 
them, the wooden disk being replaced by an iron case, in the bell- 
shaped cheeks of which the fibre-bundles are secured by means 
of strong nuts. Before use it is advisable to saturate the fibre- 
bundles with oil in order to deprive them of their brittleness, and 
thus improve their lasting quality. 

The grinding lathe, Fig. 63, is provided with such a fibre- 
brush ; it can, of course, be just as well placed upon the conical 
spindles of double machines. The iron case is provided w T ith a 
conical hole corresponding exactly to the conical spindle, the large 



TREATMENT OF METALLIC ARTICLES. 



Ill 



frictional surface preventing the turning of the brush upon the 
spindle or its running off. 



Fig. 63. 




In regard to grinding the various metals the procedure, accord- 
ing to the hardness of the metal, is as follows : — 

Iron and steel articles are first ground upon the roughing wheel, 
then fine ground upon the medium wheel, and finally upon the 
fine wheel or brushed with emery with the circular-brush. Very 
rough iron surfaces may first be ground upon solid emery wheels 
before being worked upon the roughing wheel. For depressed 
surfaces which cannot be reached with the large emery disks, 
small disks of walrus hide coated, with glue and emery are placed 
upon the point of the spindle of the polishing lathe (see Fig. 66). 

Brass and copper castings are first ground upon roughing wheels, 
which have lost part of their sharpness, and will no longer attack 
iron; they are then ground fine upon the medium wheel, and 
finally polished upon cloth or felt disks (bobs). (See p. 112 under 
Polishing.) 

Sheets of brass, German silver, and copper, as furnished by roll- 
ing-mills, are only brushed with emery and then polished with 
Vienna lime or rouge upon bobs. 

Zinc castings, as, for instance, those produced in lamp factories, 



112 



ELECTRO-DEPOSITION OF METALS. 



Fig. 64. 



are first thoroughly brushed by means of circular brushes and 
emery, and then polished upon cloth bobs. 

Sheet zinc is only polished with Vienna lime and oil upon cloth 
bobs secured to the spindle shown in Fig. 67. 

Polishing. — As will be seen from the foregoing polishing serves 
for making the articles ready, i. e., the final lustre is imparted to 
them upon soft polishing disks with the use of fine polishing 
powders. The polishing disks or bobs of fine felt, shirting or 
cloth, are secured to the polishing lathe, and, according to the 
hardness of the metal to be polished, make 2000 to 2500 revolu- 
tions per minute. A foot-lathe, such 
as shown in Fig. 64, makes generally 
not over 1800 revolutions per minute. 
Cloth bobs are made by placing pieces 
of cloth one upon another in the man- 
ner described under "Nickeling of 
sheet zinc," cutting out the centre cor- 
responding to the diameter of the spin- 
dle, and securing the disks of cloth by 
means of nuts between two wooden 
cheeks upon the spindle of the polish- 
ing lathe. In place of cloth bobs, 
solid round disks of felt or wooden 
disks covered with a layer of felt may 
be used, especially for polishing smooth 
objects without depressions, the fine- 
ness and softness of the felt depending on the degree of polish to 
be imparted, and the hardness of the metal to be manipulated. 

Double polishing lathes, according to the American patterns 
(Figs. 65 and Q6), are used for polishing objects of not too large 
dimensions, while the lathe shown in Fig. 67 serves chiefly for 
polishing large sheets, the latter being placed upon a smooth 
wooden support which rests upon the knees of the workman, as 
will be described later on in speaking of the nickeling of sheet 




zinc. 



Fig. 66 shows a double polishing lathe of larger size ; it carries 
on one side a large felt disk and a small brush, and upon the 



TREATMENT OF METALLIC ARTICLES. 

Fig. 65. 



113 




Fig. 66. 




other a circular brush and a small walrus-hide buff. The spindle 
of the small polishing lathe, Fig. 65, carries a cloth bob. 



Fig. 67. 




Self-acting polishing lathes for sheet-metal will be discussed 
under " Nickeling of sheet zinc." 



114 ELECTRO-DEPOSITION OF METALS. 

According to the hardness of the material to be polished, ferric 
oxide (colcothar or rouge), tripoli, Vienna lime, etc., in the state 
of an impalpable powder, and generally mixed with oil, or some- 
times with alcohol, are used as polishing agents. For hard metals 
an impalpable rouge of great hardness (No. F of commerce) is 
employed ; for softer metals a softer rouge (No. FFF) or Vienna 
lime, tripoli, etc. 

It is of advantage to mix the rouge with melted wax and a 
small quantity of tallow, and cast the mixture in moulds with the 
use of strong pressure. The sticks thus formed are sufficiently 
greasy to render the use of oil superfluous. In order to impregnate 
the surface of the polishing bob with the polishing material, hold 
one of the sticks for a second against the revolving disk, and then 
polish the objects by pressing them against the disk diligently 
moving them to and fro. The polishing bob must not be too 
strongly impregnated with rouge since a surplus, instead of cut- 
ting well, smears. In polishing with Vienna lime it is advisable 
to moisten the objects to be polished with oil, while the polishing 
bobs are saturated with the lime by holding a piece of it against 
them. 

Another process of polishing, called burnishing, is executed by 
tools usually made of steel for the first or grounding process, or 
of a very hard stone, such as agate or bloodstone, for finishing. 
Burnishing is applied to the final polishing of depositions of the 
noble metals. 

2. Mechanical treatment during and after the electroplating pro- 
cess. — In this connection scratch brushing the depositions will be 
first considered, its object being, on the one hand, to promote the 
regular formation of certain depositions ; on the other, to effect a 
change in the physical properties of the depositions, and, finally, 
to ascertain whether the depositions adhere to the metallic base. 

If it is seen by the irregular formation of the deposition that 
the metallic base has not been cleansed with sufficient care by the 
preparatory scratch-brushing, the object has to be taken from the 
bath and the defective places again scratch-brushed with the appli- 
cation of water and sand or pumice stone, when the object, after 
being again pickled, is replaced in the bath. 

On the other hand, electro-deposited metals are always more or 



TREATMENT OF METALLIC ARTICLES. 115 

less porous, having, so to say, a net-like structure, though it may 
not be visible to the naked eye. By scratch-brushing the meshes 
of the net are made closer by particles of metal being forced into 
them by the brush, and the deposition is thus rendered capable of 
receiving additional layers of metal. Furthermore by scratch- 
brushing the dead depositions acquire a certain lustre which is 
enhanced by the subsequent polishing process. Finally by an 
unsparing application of the scratch-brush, it will best be seen, 
whether the union of the deposition with the metallic base is suffi- 
ciently intimate to stand the subsequent mechanical treatment in 
polishing without becoming detached. 

According to the object in view, and the hardness of the depo- 
sition to be manipulated, scratch-brushes of steel or brass wire 
are chosen ; for nickel which, as a rule, requires scratch-brushing 
least and chiefly only for the production of very thick depositions, 
steel wire of 0.2 millimetre thickness is taken, for depositions of 
copper, brass and zinc, brass wire of 0.2 millimetre, fur silver, 
brass wire of 0.15 millimetre, and for gold, brass wire of 0.07 to 
0.1 millimetre. Scratch-brushing is seldom done dry; the tool 
as well as the pieces must be constantly kept wet with liquids, 
especially such as produce a froth in brushing, for instance, water 
and vinegar, or sour wine, or solutions of cream of tartar or alum, 
when it is desired to brighten a gold deposit which is too dark ; 
but that most generally used is a decoction of licorice root, of 
horse chestnut, of marsh mallow, of soap wort or of the bark of 
Panama wood, all of which being slightly mucilaginous, allow of 
a gentle scouring with the scratch-brush, with the production of 
an abundant froth. A good adjunct for scratch-brushing is a 
shallow wooden tub containing the liquid employed, with a board 
laid across it nearly level with the edges which, however, project 
a little above. This board serves as a rest for the pieces. 

The hand scratch-brush, when operating upon small objects, is 
held by the workman in the same manner as a paint brush and is 
moved over the object with a back and forward motion imparted 
by the wrist only, the forearm resting on the edge of the tub. 
For larger objects, the workman holds his extended fingers close 
to the lower part of the scratch-brush, so as to give the wires a 
certain support, and, with raised elbow, strikes the pieces re- 



116 



ELECTRO-DEPOSITION OF METALS. 



peatedly, at the same time giving the tool a sliding motion. When 
a hollow is met with, which cannot be scoured longitudinally, a 
twisting motion is imparted to the tool. 

The lathe brush (Fig. 68), is mounted upon a spindle, and is 
provided above with a small reservoir to contain the lubricating 

Fisr. 68. 




fluid, a small pipe with a tap serving to conduct the solution from 
this to a point immediately above the revolving brush. The top 
of the brush revolves towards the operator, who presents the 
object to be scratch-brushed to the bottom. The brush is sur- 
rounded by a wooden cage or screen to prevent splashing. To 
protect the operator against the water projected by the rapid 
motion, there is fixed to the top of the frame a small inclined 
board, which reaches a little lower than the axis of the brush 
without touching it. This board receives the projected liquid, 



TREATMENT OF METALLIC ARTICLES. 117 

and lets it fall into a zinc trough which forms the bottom of the 
box. Through an outlet provided in one of the angles of the 
trough a gum tube conveys the waste liquid to a reservoir below. 
After scratch brushing every trace of the lubricating liquid must 
be washed away before placing or replacing the objects in the 
bath. 

The finished electro-plated objects are first rinsed in clean water 
to remove the solution constituting the bath adhering to them ; 
they are next immersed in hot water where they remain until 
they have acquired the temperature of the water, and are then 
quickly rubbed with dry hot sawdust. It is best to use sawdust 
of soft wood free from tannin, such as maple, poplar, or pine ; 
oak sawdust is not suitable for the purpose on account of its 
content of tannin, which imparts a dirty coloration to the electro- 
depositions. The sawdust must be freed from coarser particles 
of wood by sifting. For holding the sawdust a zinc box with 
double bottom is frequently used, which is heated by waste steam 
or some other process. In order to remove all moisture from the 
pores it is advisable to place plated objects of iron and steel for a 
few hours in an oven heated to between 140° and 175° F. A 
very good method of freeing nickeled iron objects from all 
moisture which may have collected in the pores is to immerse 
them for about ten minutes in boiling linseed oil, and after allow- 
ing them to drain off, to remove the adhering oil by rubbing with 
sawdust. According to some electro-platers the deposition of 
nickel thus treated loses its brittleness and will stand bending 
several times, for instance, wire, sheets — without breaking. Ex- 
periments made by Dr. George Langbein, did not confirm these 
statements, but the security against rust of the nickeled iron 
objects was found to be considerably enhanced by boiling in 
linseed oil. 

The dry electro-plated objects are finally polished which is 
effected upon polishing bobs of fine felt, cloth, or flannel, with 
the use of fine rouge, Vienna lime, tripoli, etc., or by burnishing. 

Nickel deposits are almost without exception polished upon 
cloth or felt bobs with rouge or Vienna lime and oil. Copper 
and brass deposits are polished with fine flannel bobs, the polish- 
ing powder being applied very sparingly. Deposits of tin are 



118 



ELECTRO-DEPOSITION OF METALS. 



generally only scratch-brushed, it being impossible to impart 
great lustre to this metal by polishing with bobs ; after drying 
the deposit is polished with whiting. Deposits of gold and 
silver as well as of platinum, are polished by burnishing, the 
steel burnisher being used for the grounding process, and an 
agate or bloodstone burnisher for finishing. The operation of 
burnishing is carried on as follows : Keep the tool continually 
moistened with soap-suds. Take hold of the tool very near to 
the end, and lean very hard with it on those parts which are to 
be burnished causing it to glide by a backward and forward 
motion without taking it off the piece. When it is requisite that 
the hand should pass over a large surface at once without losing 
its point of support on the work bench, be careful in taking hold 
of the burnisher to place it just underneath the little finger. By 
these means the work is done more quickly and the tool is more 

Fig. 69. 



solidly fixed in the hand. The burnishers are of various shapes 
to suit the requirements of different kinds of work, the first rough 
burnishing being often done by instruments with comparatively 
sharp edges, while the finishing operations are accomplished 



TREATMENT OF METALLIC ARTICLES. 119 

with rounded ones. Fig. 69 illustrates the most common forms 
of burnishers of steel and agate. Both must be free from 
cracks and highly polished. To keep them free from blemishes 
they are from time to time polished by vigorously rubbing them 
with fine tin putty, rouge or calcined alum upon a strip of leather 
fastened upon a piece of wood which is placed in a convenient 
position upon the work bench. 

The objects polished with Vienna lime and oil, or with rouge, 
have to be freed from adhering polishing dirt which, with flat 
smooth objects, is effected by wiping with a flannel rag and Vienna 
lime, and in those with depressions or dead surfaces by brushing 
with a soft brush and soap-water and then drying in sawdust. 

B. Chemical Treatment. 

While the preparation of a pure metallic, and at the same time, 
smoother surface is the aim of the mechanical treatment, the 
chemical preparation of the objects serves, on the one hand, 
the purpose of facilitating the mechanical treatment by soften- 
ing and dissolving the impure surface, and, on the other, of free- 
ing the mechanically prepared objects from adhering oil, grease, 
dirt, etc., so as to bring them into the state of absolute purity re- 
quired for the electroplating process. 

Pickling. — The composition of the pickling fluid varies accord- 
ing to the nature of the metal which is to be pickled. 

Cast iron and wrought iron objects are pickled in a mixture of 

1 part by weight of sulphuric acid of 66° Be. and 15 of water; 
hydrochloric acid may be substituted for the sulphuric acid. 

An excellent pickle for iron is obtained by mixing 10 quarts 
of water with 28 ozs. of concentrated sulphuric acid,* dissolving 

2 ozs. of zinc in the mixture and adding 12 ozs. of nitric acid. 
This mixture makes the iron objects bright, while they become 
black in dilute sulphuric or hydrochloric acid. 

To cleanse badly rusted iron objects without attacking the iron 
itself, it is recommended to pickle them in a concentrated solution 

* The acid should he poured into the water, and not the water into the 
acid. 



120 ELECTEO-DEPOSITION OF METALS. 

of chloride of tin, which however should not contain too much 
free acid, as otherwise the iron is attacked. 

The duration of pickling depends on the more or less thick 
layer of scale, etc., which is to be removed or softened ; the 
process may be considerably assisted and the time shortened by 
frequent scouring with sand or pumice. The pickled articles are 
rinsed in cold water, then immersed in hot water, and dried in 
sawdust. In order to neutralize the acid remaining in the pores, 
it is advisable to make the rinsing water alkaline by the addition 
of caustic potash or soda, etc. 

Zinc objects are only pickled when they show a thick layer of 
oxide, in which case pickling is also effected in dilute sulphuric 
or hydrochloric acid, and brushing with fine pumice. A very 
useful pickle for zinc consists of sulphuric acid 100 parts by 
weight, nitric acid 100, and common salt 1. The zinc objects 
are immersed in the mixture for one second, and then quickly 
rinsed off in water, which should be frequently changed. 

Copper and its alloys, brass, bronze, tombac, and German silver, 
are cleaned and brightened by dipping in a mixture of nitric 
acid, sulphuric acid, and lamp black, a suitable pickle consisting 
of sulphuric acid, of 66° Be., 50 parts by weight, nitric acid, of 
36° Be., 100, common salt 1, and lamp black 1. In order to 
remove the brown coating, due to cuprous oxide, the objects are 
first pickled in dilute sulphuric acid, and then dipped for a few 
seconds, with constant agitation, in the above-mentioned pickle 
until they show a bright appearance. They are then immediately 
rinsed in water to check any further action of the pickle. 

If objects of copper or its alloys are not to be subjected, after 
pickling, to further mechanical treatment or are to be at once 
placed into the electrolytic bath, it is best to execute the pickling 
process in two operations by treating them in a preliminary pickle 
and brightening them in the bright-dipping bath. The prelimi- 
nary pickle consists of nitric acid, of 36° Be., 200 parts by weight, 
common salt 1, lamp black 2. In this preliminary pickle the 
articles are allowed to remain until all impurities are removed, 
when they are rinsed in a large volume of water, dipped in boil- 
ing water so that they quickly dry, and plunged into the bright- 
dipping bath, which consists of nitric acid, of 40° Be., 75 parts 



TREATMENT OF METALLIC ARTICLES. 121 

by weight, sulphuric acid, of 66° Be., 100, and common salt 1. 
It is uot advisable to bring the objects which have passed through 
the preliminary pickle and rinsing water directly, while still moist, 
into the bright-dipping bath, since for the production of a beauti- 
ful pure lustre the introduction of water into the bright-dipping 
bath must be absolutely avoided. Hence the objects treated in 
the preliminary pickle should first be dried by heating in hot 
water and shaking the latter off. 

Potassium cyanide, dissolved in ten times its weight of water, 
is often used instead of the acid pickle for brass, especially when 
it is essential that the original polish upon the objects should not 
be destroyed, as in the preparation of objects for nickel plating. 
The objects should remain in this liquid longer than in the acid 
pickle, because the metallic oxides are far less soluble in this 
than in the latter. In all cases the final cleansing in water must 
be observed. 

All acid pickles used for different kinds of work should be kept 
distinct from each other, so that one metal may not be dipped into 
a solution containing a more electro-negative metal, which would 
deposit upon it by a chemical exchange. 

The pickled objects must not be unnecessarily exposed to the 
air and should be transferred as quickly as possible from the 
pickle to the wash waters and thence to the electrolytic bath, or 
if this is not feasible, kept under pure water. Pickled objects 
which are not to be plated are carefully washed in water, which 
should be frequently changed, rinsed, drawn through a solution 
of tartar, and dried by dipping in boiling water and rubbing with 
sawdust. 

Places soldered with soft solder, as well as parts of iron, become 
black by pickling, and have to be brightened by scouring with 
pumice or by scratch-brushing. 

It is frequently required that bright objects of brass or other 
alloys of copper should be given a dead or dull surface by pick- 
ling so that after plating they show a beautiful dead lustre. This 
may be effected in various ways. Every bright-dipping bath acts 
as a dead dip if the articles are allowed to remain in it for a longer 
time and at a higher temperature. A better effect is, however, 
produced by adding zinc sulphate (white vitriol) to the pickle, 



122 ELECTRO-DEPOSITION OF METAES. 

the deadening being the stronger, the more zinc sulphate is added. 
A good dead dip is prepared by adding a solution of 0.35 oz. of 
zinc sulphate in 3 J ozs. of water to the cold mixture of 6| lbs. 
of nitric acid, of 36° Ed, 4.4 lbs. of sulphuric acid, of 66° Be., 
and J oz. of common salt. According to the shade desired, the 
articles are left in this mixture for 2 io 10 minutes, and as they 
come from it with a faded earthy appearance, they are plunged 
momentarily into a bright-dipping bath, whereby they acquire 
a dead lustre, and are then quickly rinsed in a large volume of 
clean water. 

Generally speaking it may be said that less depends on the 
composition of the pickle than on quick and skilful manipula- 
tion ; and as good results have always been obtained with the 
above-mentioned mixture, there is no reason for repeating the 
innumerable receipts given for pickles. The main points are to 
have the acid mixture as free from water as possible, further the 
presence of hyponitric acid, which is produced by the reduction 
of nitric acid in consequence of the addition of organic substances 
(lamp black, sawdust, etc.), and of chlorine which is formed by 
the action of the sulphuric acid upon the common salt. The 
volume of the dipping bath should not be too small, since in 
pickling the acid mixture becomes heated and the increased tem- 
perature shows a very rapid, frequently not controllable, action, 
so that a corrosion of small articles may readily take place. It 
is therefore necessary to allow the acid mixture, after its prepa- 
ration, to thoroughly cool off; pour the sulphuric acid into the 
nitric acid (never the reverse ! !), and allow the mixture, which 
thereby becomes strongly heated, to cool off to at least the ordi- 
nary temperature. 

In order to be sure of the uniform action of the pickle upon 
all parts, it is, in all cases, advisable to free the articles previous 
to pickling from grease by one of the methods given later on. 

In pickling, abundant vapors are evolved which have an in- 
jurious effect upon the health of the workmen, and corrode metallic 
articles exposed to them. The operation should, therefore, be 
conducted in the open air, or under a well drawing vapor flue. 

In large establishments it may happen that the quantity of 
escaping acid vapors is so large as to become a nuisance to the 



TREATMENT OF METALLIC ARTICLES. 



123 



neighborhood, which the proprietors may be ordered by the autho- 
rities to abate. The evil is best remedied by a small absorbing 
plant, as follows : — 

Connect the highest point of the vapor flue D (Fig. 70), by a 
wide clay pipe R, with a brick reservoir, A, laid in cement, so 
that R enters A a few centimetres above the level of the fluid, 
kept at the same height by the discharge pipe b. Above, the 
reservoir is closed by a vault through which the water conduit W 

Fie. 70. 




is introduced. Below the sieve S, which is made of wood, and 
coated with lacquer, a wide clay pipe R l leads to the chimney of 
the steam boiler ; or the suction pipe of an injector is introduced 
in this place by which the air from the vapor flue is sucked 
through the reservoir and allowed to escape into the open air or 
into a chimney. Through the manhole 31, the sieve-bottom S x 
of the reservoir is filled with large pieces of chalk or limestone, 
the manner of operating being then as follows : A thin jet of 
water falls upon S, wher,e it is distributed and runs over the layer 
of chalk. The air of the pickling room saturated with acid vapors 
moves upwards in consequence of the draught of the chimney of 
the steam boiler, the injector or ventilator, and yields its content 



124 ELECTRO-DEPOSITION OF METALS. 

of acid to the layer of chalk, while the neutral solution of calcium 
nitrate and calcium chloride, which has been formed, runs off 
through b. 

The absorption of the acid vapors may, of course, be effected 
by apparatus of different construction ; but the one above described 
may be recommended as being simple, cheap and effective. 

The considerable consumption of acid for pickling purposes in 
large establishments makes it desirable to regain the acid and 
metal contained in the exhausted dipping baths. The following 
process has proved very successful for this purpose. Mix the old 
dipping baths with \ their volume of concentrated sulphuric acid, 
and bring the mixture into a nitric acid distilling apparatus. 
Distil the nitric acid off at a moderate temperature, condense it in 
cooled clay-coils, and collect it in glass balloons. To the residue 
in the still, add water, precipitate from the blue solution, which 
contains sulphate of copper and zinc, the copper with zinc waste, 
and add zinc until an evolution of hydrogen no longer takes place. 
Filter off the precipitated copper through a linen bag, wash and 
dry. The fluid running off, which contains zinc sulphate, is 
evaporated to crystallization, and yields quite pure zinc sulphate, 
which may be sold to dye-works, or for the manufacture of zinc- 
white. 

According to local conditions, for instance, if the zinc-sulphate 
cannot be profitably sold in the neighborhood, or zinc waste can- 
not be obtained, it may be more advantageous to omit the regain- 
ing of zinc from the dipping baths. In this case the fluid which 
is obtained by mixing the contents of the still with water is com- 
pounded with milk of lime, until it shows only a slight acid 
reaction. The gypsum formed is allowed to settle, and after 
bringing the supernatant clear fluid into another reservoir, the 
copper is precipitated by the introduction of old iron. The first 
rinsing waters, in which the pickled objects are washed, are treated 
in the same manner. The precipitated copper is washed and 
dried. 

For the production of a grained surface by pickling, a mixture 
of 1 volume of saturated solution of bichromate of potash in 
water, and 2 volumes of concentrated hydrochloric acid may be 
recommended.' The brass articles are allowed to remain in the 



TREATMENT OF METALLIC ARTICLES. 125 

mixture for several hours, when they are momentarily plunged 
into the bright dipping bath and rinsed in a large volume of 
water, which should be frequently changed. 

Removal of grease. — This operation is to be executed with the 
greatest nicety, because on it chiefly depends the success of electro- 
plating. Its object is to remove every trace of impurity, may it 
be due to touching with the hands or to the manipulation in 
grinding and polishing. 

According to the preparatory treatment of the objects, the 
removal of grease is a more or less complicated operation. Large 
amounts of oily or greasy matter should be removed by thoroughly 
rinsing in benzine, it being recommended to execute this operation 
immediately after grinding and polishing so that the oil used in 
these operations has no chance of hardening as is frequently the 
case with objects polished with Vienna lime and oil. Instead of 
cleaning with benzine, the objects, as far as their nature allows, 
may be boiled in a hot lye of 1 part of caustic potash or caustic 
soda in 10 of water, until all the grease is saponified, when the 
dirt consisting of grinding powder can be readily removed by 
brushing. In place of solutions of caustic alkalies, hot solutions 
of potash or soda may also be used, but their action is much 
slower and offers no advantages. Objects of tin, lead, and Bri- 
tannia, being attacked by the hot lye must be left in contact with 
it for a short time only. 

The articles thus freed from the larger portion of grease are 
first rinsed in water, and then for the removal of the last traces 
of grease, brushed with a bristle brush and a mixture of water, 
quicklime, and whiting, until when rinsing in water all portions 
appear equally moistened and no dry places are visible. 

The lime mixture is prepared by slaking freshly burnt lime, 
free from sand, with water to an impalpable powder, mixing 1 
part of this with 1 of fine whiting, and adding water with con- 
stant stirring until a paste of the consistency of syrup is formed. 

The shape of many objects presents certain difficulties in the 
removal of grease ; the deeper portions cannot be reached with 
the brush, as for instance, in skates which often are to be nickeled 
in a finished state. In this case the objects are drawn in succes- 
sion through three different benzine vessels ; in the first benzine 



126 ELECTEO-DEPOSITION OF METALS. 

most of the grease is dissolved, the rest in the second, while the 
third serves for rinsing off. When the benzine in the first vessel 
contains too much grease, it is emptied and filled with fresh ben- 
zine, and then serves as the third vessel, while that which was 
formerly the second becomes the first, and the third the second. 
After rinsing in the third benzine vessel, the objects are plunged 
into hot water, then for a few seconds dipped in thin milk of lime, 
and finally thoroughly rinsed in water. It is recommended not 
to omit the treatment with milk of lime of objects freed from 
grease with benzine. 

To avoid subsequent touching with the hands the objects, before 
freeing them from grease, must of course be tied to the metallic 
wires (of soft copper) by which they are suspended in the electro- 
lytic bath. In removing the grease by the wet method a layer 
of oxide scarcely perceptible to the eye is frequently formed upon 
the metals. This layer of oxide has to be removed, the liquid 
used for the purpose varying, of course, with the nature of the 
layer. 

Objects of iron and steel as well as of zinc are momentarily 
plunged in a mixture of sulphuric acid 1 part by weight and 
water 20 parts and quickly rinsed off in clean water. Highly 
polished objects of iron and steel after being treated with this 
mixture are best again rapidly brushed with lime paste and after 
rinsing off quickly, immediately brought into the electrolytic 
bath. 

Copper, brass, bronze, German silver, and tombac are best 
treated with a dilute solution of potassium cyanide, 1 part of 60 
per cent, potassium cyanide in 15 to 20 of water. The objects 
are then quickly rinsed off and placed in the electrolytic bath. 

Lead and Britannia may be treated with water slightly acidu- 
lated with nitric acid. 



PROCESSES OF ELECTRO-DEPOSITION. 127 



CHAPTER VI. 

PROCESSES OF ELECTRO-DEPOSITION. 

Next to the proper mechanical and chemical preparation of 
the objects, the success of the process of electro-deposition depends 
on the suitable composition of the electrolytic solutions (baths), 
and the correct current strength which is conducted into the bath 
for the precipitation of the metals. In regard to the latter the 
most essential conditions have already been discussed in Chap. IV., 
" Electro-plating plants in general," and will be further referred 
to in speaking of the several electro-plating processes. Hence, the 
general rules which have to be observed in the preparation of the 
baths will first be considered. 

Water being the solvent for all electrolytic baths, its constitu- 
tion is by no means of such slight importance as is frequently 
supposed. 

Spring and well water often contain considerable quantities of 
lime, magnesia, common salt, iron, etc., the presence of which may 
cause various kinds of separations in the baths ; on the other 
hand, river w T ater is frequently to such an extent impregnated with 
organic substances that its employment without previous purifica- 
tion cannot be recommended. No doubt, distilled water, or in 
want of that rain water, is the most suitable for the preparation 
of baths. However, rain water collected from metal roofs should 
not be used, nor that running off from other roofs, it being con- 
taminated with dust. Rain water should be caught in vessels of 
glass, earthenware, or wood, free from tannin, and filtered. 
Where river or well water has to be employed, thorough boiling 
and filtering before use is absolutely necessary in order to separate 
the carbonates of alkaline earths held in solution. By boiling a 
possible content of sulphuretted hydrogen is also driven off. 

Another important factor is the purity of the chemicals used 
for the baths, their premature failure being in most cases caused 



128 ELECTEO-DEPOSITION OF METALS. 

by the unsuitable nature of the chemicals, which also frequently 
gives rise to abnormal phenomena inexplicable to the operator. 
Chloride of zinc, for instance, may serve as an example. It is 
found in commerce in very varying qualities, it being prepared 
for dyeing purposes with about 70 per cent, actual content of 
chloride of zinc, for pharmaceutical use with about 90 per cent., 
and for electrolytic purposes with 98 to 99 per cent. Now it 
will readily be seen that if an operator in preparing a brass bath 
according to a formula which calls for pure chloride of zinc uses 
a preparation intended for dyeing purposes, there will be a defi- 
ciency of metallic zinc in the bath, and the content of copper in 
the bath being too large in proportion to the zinc present, will 
cause reddish shades of the deposits. 

Likewise, in case the operator uses potassium cyanide of 
low content, when the formula calls for a pure article with 98 
per cent., he will not be able to effect the solution of copper or 
zinc salts with the quantity prescribed. Furthermore, potassium 
cyanide in the preparation of which prussiate of potash, contain- 
ing potassium sulphate, is used, will cause, by reason of the for- 
mation of potassium sulphocyanide, various disturbing influences 
(formation of bubbles in the deposit), the explanation of which 
is difficult to the operator, who, trusting to the purity of the 
chemicals, seeks elsewhere for the causes of the abnormal phe- 
nomena. 

Or, if in preparing nickel baths, a salt containing copper is 
used, the nickeling will never be of a pure white color, but 
show shades having not even a distinct resemblance to the color 
of nickel. 

The above-mentioned examples suffice to show how careful the 
operator must be in the selection of the sources from which he 
obtains his supplies. It may here be mentioned that all the 
directions given in the following pages refer to chemically pure 
products ; where products of a lower standard may be used, the 
content is especially given. 

For the concentration of the various baths, no general rules 
can be laid down ; neither can the determination of the density 
of the baths by the aerometer be relied on. If the electrolytic 
solutions consisted of nothing else but the pure metallic salts, the 



PROCESSES OF ELECTRO-DEPOSITION. 129 

specific gravity, which is indicated by the aerometer-degrees, might 
serve for an estimation of their value. But such an estimation 
is often apt to prove deceptive, since to decrease the resistance, 
the baths also require conducting salts, and by the addition of a 
larger quantity of them, the specific gravity of a bath may be 
increased to any extent without the content of the more valuable 
metal being greater than in a bath showing fewer aerometer- 
degrees. 

An electrolytic bath should not be poor in metal, as otherwise it 
soon becomes exhausted, and besides the deposits form more slowly 
than in a bath with a correct content of metal ; on the other hand, 
the bath must not be too concentrated, as, in this case, salts in the 
form of crystals readily separate and deposit themselves upon 
the anodes, the sides of the vessels, and even upon the articles 
themselves, which may cause holes to form in the deposit ; or the 
crystals envelop the anodes so tightly that the current cannot reach 
the bath. Besides, too concentrated baths generally produce dis- 
colored deposits, as, for instance, too concentrated nickel baths, 
which yield a dark and spotted deposit. 

Hence in summer, when the bath has a higher temperature, it 
may be made more concentrated than in winter. If crystals are 
separated out, even when the bath shows a temperature of 58° F., 
it must be diluted with water until the formation of crystals ceases, 
after those which have been formed have been dissolved in hot 
water and added to the bath. 

In order that all strata of the bath may show an equal content 
of metal, it is advisable in the evening, after the day's work is 
done, to thoroughly stir up the solution with a wooden crutch. 
For practical reasons the baths are generally made one-quarter 
to one-third deeper than corresponds to the length of the objects 
to be plated. In consequence of this, the strata of fluid between 
the anodes and the objects become poorer in metal than those on 
the bottom, and the object of stirring up is to restore the same 
concentration to all portions of the bath. 

The strata of fluid which come in contact with the anodes 
become, by the absorption of metal, specifically heavier than the 
other strata, and sink to the bottom ; on the other hand, the 
strata of fluid which yield metal to the objects, become specifically 




130 ELECTRO-DEPOSITION OF METALS. 

lighter and rise to the top. A partial compensation of course 
takes place by diffusion, but not a complete one, and from 
this cause arise several evils. The heavier and more saturated 
fluid, offering greater resistance to the current, the anodes are 
attacked chiefly on the upper portions where the specifically 
lighter layer of fluid is ; practically this is proved by the appear- 
ance of the anodes which, at first square, after being 
Fig. 71. for some time used, assume the shape shown in 
Fig. 71. 

On the other hand, the portions of the cathodes 
(objects) which come in contact, near the surface, 
with strata of fluid poorer in metal, acquire a deposit 
of less thickness than the lower portions which dip into 
the bath where it is richer in metal. Now if the 
bath also contains free acid and if there is a con- 
siderable difference in the specific gravity of the 
lower and upper strata of fluid, the electrode, which 
touches both strata, produces a current, the effect of which is that 
metal dissolves from the upper portions and deposits upon the 
lower. This explains the phenomenon that a deposit on the 
upper portions of the objects may be redissolved, even when a 
current which, however, must be very weak, is conducted into the 
bath from an external source. 

Many authors, therefore, go so far as to demand that during the 
electroplating process the baths should be kept in constant agita- 
tion by mechanical means. This, however, is scarcely necessary, 
because a homogeneity of the solution is to a certain extent effected 
by the agitation of the fluid in suspending and taking out the 
objects. Hence as long as objects are put in and taken out an 
agitation naturally takes place in which all the strata of fluid 
between the objects and anodes take part, while only the deepest 
strata, which do not come in contact with the objects and the 
anodes, remain in a state of stagnation. 

Constant agitation of the electrolytic solution is of advantage 
only in silvering and in the galvano-plastic reproduction in the 
acid copper bath, in which the objects have to remain four to five 
and eight to ten hours. Some authors demand constant agitation 
for the more rapid removal of the bubbles of hydrogen which 



PROCESSES OF ELECTRO-DEPOSITION. 131 

form on the objects ; but the same end is attained without com- 
plicated contrivances, by the operator accustoming himself to 
strike the object-rod a slight blow with the finger each time he 
suspends an object. 

The degree of temperature required for the electrolytic solu- 
tions has already been discussed on page 76, where also the means 
have been given by which too cool solutions may be brought to 
the proper degree of temperature. Baths which are to be used cold 
should under no circumstances show a temperature below 59° F., 
it being best to maintain them at between 64.5° and 68° F. 

Boiling is required in the preparation of many baths if, after 
cooling, they are to yield good and certain results. The boiling 
is best effected in enamelled iron kettles, or with small baths, in 
porcelain or earthenware dishes or pots. The enamel of the iron 
kettles must be of a composition which is not attacked by the 
bath. The use of metal vessels should be avoided ; copper and 
brass baths may, however, be boiled in strong copper kettles, though 
they are somewhat attacked. A copper kettle, after being freed 
from grease and scoured bright, may be provided with a thick 
deposit of nickel, by filling it with a nickel bath, connecting it 
with the negative pole of a strong battery or dynamo machine, 
and suspending in it a number of nickel anodes connected with 
the positive pole. Such a nickled kettle may be used for boiling 
nickel baths, but enameled kettles or large dishes of nickel sheet 
deserve the preference. 

If the boiling of large quantities of fluid is not convenient, 
the same end may be attained by thoroughly working the bath 
for a few days with the electric current. Suspend to the anode- 
rods, as many anodes as possible, secure to the object-rods a few 
plates of the same metal, and introduce a current of medium 
strength, until an object, from time to time, suspended in the bath 
acquires a regular deposit. This method is frequently and very 
successfully used for large brass baths. 

If nickel salts, dissolving with difficulty, have to be dissolved 
for the preparation of nickel baths, and a suitable kettle for the 
purpose be wanting, boil clean water in a brightly scoured copper 
kettle ; pour the boiling water into a clean wooden bucket hold- 
ing from eight to ten quarts ; add the corresponding quantity of 



J 32 ELECTRO-DEPOSITION OF METALS. 

nickel salt, and stir with a stick of wood until solution is com- 
plete. 

For large baths this method consumes too much time, and it is 
better to use a large oval or round wooden vat, which is provided 
with a coil of lead, and to bring the contents of the vat to boil- 
ing by introducing steam into the coil. 

If the prepared and boiled solutions are not entirely clear, they 
have to be filtered, which for large baths is best effected with bags 
of fine felt ; and for smaller baths, especially those of the noble 
metals, with filtering paper. 

To secure lasting qualities to the baths, they must be carefully 
protected from every possible contamination. When not in use 
for plating they should be covered to keep out dust. The objects 
before being placed in the bath should be free from adhering 
scouring material or dipping fluid, which otherwise might, in time, 
spoil the bath. The cleansing of the anode and object rods by 
means of sand paper, or emery paper, should never be done over 
the bath, so as to avoid the danger of the latter being contaminated 
by the oxides of the metal, constituting the rods, falling into it. 
When a visible layer of dust has collected upon the bath, it must be 
removed, as otherwise particles of dust might deposit upon the arti- 
cles and prevent an intimate union of the deposit with the basis- 
metal. With large baths the removal of the layer of dust is 
readily effected by drawing a large piece of filtering or tissue 
paper over the surface, and repeating the operation with fresh 
sheets of clean paper, until all the dust is removed. Small baths 
should be filtered. 

The choice of anodes is also an important factor for keeping 
the baths in good condition, as well as for obtaining good results. 
The anodes should always consist of the metal which is deposited 
from the solution ; and the metal used for them must be pure and 
free from all admixtures. To replace as much as possible the 
metal withdrawn from the bath by the electro-plating process, the 
anodes must be soluble ; and it is wrong, if, for instance, nickel 
baths are charged with insoluble anodes of carbon ; or for smaller 
baths, of sheet platinum. Such insoluble anodes cause a steady 
and rapid declination in the content of metal, an excessive forma- 
tion of acid in the bath, and by the detachment of particles of 



PROCESSES OF ELECTRO-DEPOSITION. 133 

carbon, a contamination of the solution. Further particulars in 
regard to anodes will be given in discussing the separate baths. 

When upon a pure metallic surface another metal is electro- 
deposited, the first portion of the deposit penetrates into the basis- 
metal, thus forming an alloy. This may be readily proved by 
repeating Gore's experiments : If a thick layer of copper be pre- 
cipitated upon a platinum sheet, and then heated to a dark red 
heat, the deposit can be entirely peeled off; by then heating the 
platinum sheet with nitric acid, and thoroughly washing with 
water, it appears, after drying, entirely white and pure. By re- 
heating the sheet, the surface becomes again blackened by cupric 
oxide, and by frequently repeating the same operations, a fresh 
film of cupric oxide will always be obtained. 

This penetration of the deposit into the basis-metal, however, 
does not merely take place during electro-plating but also later 
on, and it may frequently be observed that, for instance, zinc 
objects only slightly coppered or brassed, after some time, become 
again white. Since this also happens when the deposits are pro- 
tected by a coat of lacquer against atmospheric influences, the 
only explanation of the phenomenon can be that the deposit is 
absorbed by the basis-metal, which is also confirmed by analysis. 
This fact must be taken into consideration if durable deposits are 
to be produced. 

To guarantee good performance an electrolytic bath must fulfil 
the following conditions : — 

1 . It must possess good working capacity. 

2. It must exert a sufficiently dissolving action upon the anode. 

3. It must reduce the metal in abundance and in a reguline 

state. 

4. It must not be chemically decomposed by the metals to be 

plated, hence not by simple immersion ; the adherence of 
the deposit to the basis-metal being in this case impaired. 

5. It must not be essentially decomposed by air and light. 

Reduction of metals without a battery (electro-deposition by contact)- 

We may here appropriately mention the reduction of metals 
which takes place by the contact of two metals in a fluid without the 



134 ELECTRO-DEPOSITION OF METALS. 

aid of an exterior source of current. That an electric current is 
thereby generated has been previously explained ; one metal, by 
coming in contact with a more electro-positive one, becomes 
electro-negative and decomposes the fluid. If the latter is a 
metallic solution, and the metal contained in it not more strongly 
electro-negative than the negatively excited metal, a separation 
of metal takes place in consequence of decomposition. This pro- 
cess is termed electro-deposition by contact. Generally the metals 
which are to be coated are brought in contact with a bright rod of 
zinc, the latter being a highly electro-positive metal. The zinc 
is allowed to dip in only so far as to secure a sure contact with 
the metal to be coated. 

The contact of one metal with two fluids, or that of two metals in 
tivo fluids presents similar phenomena ; an electric current with visi- 
ble action manifests itself, and in the latter case we have a complete 
element. By dipping the more electro-negative metal in a metallic 
solution whose metal is not more electro-negative, the metal sepa- 
rates from the solution upon the metallic strip dipping in. While 
by the contact of one metal with another in one fluid, only thin de- 
posits can be produced, and by coating the electro-negative metal 
with the separated metal the contact-current loses some of its 
original strength, by immersing two metals in two fluids, deposi- 
tions of considerable thickness can under certain conditions be 
produced, as, for instance, with the galvano-plastic cell apparatus, 
which will be discussed later on. 

A reduction of metal can also be brought about by dipping one 
metal into one fluid. This may take place in consequence of the 
simple solution of the metal dipped in, and hence the separation 
may be conceived as a simple chemical action. In how far electric 
currents manifest themselves and co-operate thereby is still unde- 
cided ; we only know that the electro-positive metals, such as zinc, 
tin, iron, copper, can reduce the electro-negative metals, such as 
mercury, silver, gold, etc., from the solutions of their salts, and 
that the reduction is the more rapid and the stronger the more 
electro-positive is the metal dipped in, and the more electro- 
negative the dissolved metal. 

Upon this action depend coppering, silvering, gilding, etc., by 
immersion. 



DEPOSITION OF NICKEL AND COBALT. 135 



CHAPTER VII. 

DEPOSITION OF NICKEL AND COBALT. 

1. Nickeling. 

Though nickel-plating is of comparatively recent origin, it 
shall be first described, since, chiefly by reason of the development 
of the dynaino-electrical machine, it has steadily grown in popu- 
larity and become an industry of great magnitude and importance. 
The great popularity which nickel-plating enjoys is due to the 
excellent properties of the nickel itself; the almost silvery white- 
ness of the metal ; its cheapness as compared with silver ; the 
hardness of the electro-deposited metal, which gives the coating 
great power to resist wear and abrasion ; its capability of taking 
a high polish ; the fact that it is not blackened by the action of 
sulphurous vapors which rapidly tarnish silver, and finally the 
fact that it exhibits but little tendency to oxidize even in the 
presence of moisture. 

Properties of nickel. — Pure nickel is a lustrous, silvery white 
metal with a slight steel gray tinge. It is hard, malleable and 
ductile. Its specific gravity varies from 8.3 (cast nickel plates) 
to 9.3 (wrought or rolled plates). It melts at about the same 
temperature as iron, but is more fusible when combined with 
carbon. It is slightly magnetic at ordinary temperatures, but 
loses this property on heating to 680° F. 

The metal is soluble in dilute nitric acid, concentrated nitric 
acid rendering it passive, i. e., insoluble. In hydrochloric and 
sulphuric acids it dissolves very slowly, especially when in a 
compact state. 

Certain articles, for instance, hot fats strongly attack nickel, 
while vinegar, beer, mustard, tea, and other infusions produce 
stains ; hence, the nickeling of culinary utensils or the use of nickel- 
plated sheet iron for culinary utensils cannot be recommended. 

The chemical equivalent of nickel is 29.5. 



136 ELECTRO-DEPOSITION OF METALS. 

Nickel baths. — The first requisite in preparing nickel baths is 
the use of absolutely pure chemicals, and in choosing the nickel 
salts to be especially careful that they are free from salts of iron, 
copper and other metals. Furthermore, it is not indifferent what 
kind of nickel salt is used, whether nickel chloride, nickel sul- 
phate, the double sulphate of nickel and ammonium, etc., but the 
choice of the salt depends chiefly on the nature of the metal 
which is to be nickeled. There are a large number of general 
directions for nickel baths, of which nickel chloride, ammonio- 
nickel chloride, nickel nitrate, etc., form the active constituents, 
and yet it would be a grave mistake to use these salts for nickel- 
ing iron, because the liberated acid, if not immediately and com- 
pletely fixed by the anodes in dissolving, imparts to the iron 
objects a great tendency to the formation of rust. Iron objects 
nickeled in such a bath, to be sure, come out faultless, but in a 
short time, even if stored in a dry place, portions of the nickel 
layer will be observed to peel off, and by closely examining such 
objects it will be seen that under the deposit of nickel a layer of 
rust has formed which actually tears the nickel off. The use of 
nickel sulphates or of the salts with organic acids is, therefore, 
considered best. It might be objected that the liberated sulphuric 
acid produces in a like manner a formation of rust upon the iron 
objects, but according to long experience and many thorough 
examinations such is not the case, the tendency to the formation 
of rust being only imparted by the use of the chloride and nitrate. 
The use of nickel salts with organic acids is in many cases more 
advantageous than that of the sulphates, but such salts are con- 
siderably dearer, and hence, they are more seldom employed ; in 
many prepared nickeling salts they form the active constituent. 
The composition of the conducting salts requires the same delibera- 
tion as that of the nickeling salts. To decrease the resistance of 
the nickel solutions, conducting salts are added to them, which 
are also partially decomposed by the current. Like the use of 
nickel chloride, in nickeling iron, an addition of ammonium 
chloride which is much liked cannot be recommended, though 
the subsequent easy reduction of nickel invites its employment. 

For copper and its alloys, zinc, etc., the chlorine combinations 
may be used, but for nickeling iron they must be avoided as -the 



DEPOSITION OF NICKEL AND COBALT. 137 

source of future evils. The use of sodium sulphide, sodium 
nitrate, barium oxalate, ammonium nitrate, sodium sulphate, and 
ammonium alum as conducting salts, which has been recommended 
by various authors, is unsuitable. With few exceptions, which 
will be given later on, the best basis for the conducting salt, 
according to Bottger and Adams, is ammonia, especially in the 
form of ammonium sulphate or hydrochlorate, provided the latter 
is not used for baths for nickeling iron. 

Some other additions to the nickeling bath, which are claimed 
to effect a pure silvery-white reduction of the nickel, have been 
recommended by various experts. Thus the presence of small 
quantities of organic acid has been proposed, for instance, boric 
acid by Weston, benzoic acid by Powell, and citric acid or acetic 
acid by others. The presence of small quantities of a free acid 
effects without doubt the reduction of a whiter nickel than is 
the case with a neutral or alkaline solution. Hence a slightly 
acid reaction of the nickeling bath, due to the presence of citric 
acid, etc., with the exclusion of the strong acids of the metal- 
loids, can be highly recommended. The quantity of free acid 
must however not be too large, as this would cause the deposit 
to peel off. 

Boric acid, recommended by Weston as an addition to nickeling 
and all other baths, has a favorable effect upon the pure white 
reduction of the nickel, especially in nickeling rough castings, 
i. e., surfaces not ground. Weston claims that boric acid pre- 
vents the formation of basic nickel combinations on the objects, 
and that it makes the deposition of nickel more adherent, softer 
and more flexible. Whether with a correct current- strength, 
basic nickel salts, to which the yellowish tone of the nickeling is 
said to be due, are separated on the cathode, is not yet proved, 
and would seem more than doubtful. The action of the boric 
acid has not yet been scientifically explained, but numerous ex- 
periments have shown that the deposition of nickel from nickel 
solution containing boric acid, is neither more adherent, nor softer 
and more flexible than that from a solution containing small quan- 
tities of a free organic acid. Just the contrary, the deposition is 
harder and more brittle in the presence of boric acid, and differ- 
ent results may very likely be due to the employment of currents 



138 ELECTKO-DEPOS^TION OF METALS. 

of varying strength. A weak current always and under all con- 
ditions causes the deposition of a harder and more brittle nickel 
than a current of medium strength, and in order to judge the 
quality of the deposited nickel from baths of varying composi- 
tion, the surface of the objects and of the anodes must always be 
the same, and currents of equal quantity and electromotive force 
be conducted into the bath. Weston's bath will be spoken of 
later on ; Powell's proposition for the use of benzoic acid need 
scarcely be taken seriously, since the results from baths contain- 
ing it differ in no respect from those without it. 

Before giving suitable formulae for the composition of nickel 
baths, it will be necessary to discuss the means of determining their 
acidity and alkalinity. As previously mentioned, a nickel bath 
to yield a beautiful white deposit should contain only a small 
quantity of free acid ; too much acid preventing the firm adherence 
of the deposit, while alkaline and even neutral baths do not 
yield nickel of a pure white color but of a somewhat darker 
tone. A bath is neutral when it contains neither free acid nor 
free alkali, which is recognized by neither blue nor red litmus 
paper* being changed by the solution. Blue litmus paper is 
colored red by acid fluids, and red litmus paper blue by alkaline 
fluids. By simultaneously dipping one-half of a strip of blue 
and of red litmus paper in the solution, the reaction of the fluid 
can be judged from the change in color and the rapidity and 
intensity of its appearance. If a bath, which like most nickel 
baths is to work with only a slight reaction, immediately and 
intensely reddens blue litmus paper, a suitable alkali has to be 
added until the coloration of a fresh strip of litmus paper appears 
slower and less intense. If, on the other hand, the test shows 
that red litmus paper becomes blue, and that consequently the 
bath is alkaline, a slight acid reaction is restored by the gradual 
addition of citric acid or another acid suitable to the composition 
of the baths. Baths made with boric acid form an exception ; 
and must work with a strong acid reaction. 

I. The most simple nickel bath consists of a solution of 8 to 10 

* Blue and red litmus paper must be kept, each by itself, in well-closed 
glass jars. 



DEPOSITION OF NICKEL AND COBALT. 139 

parts by weight of pure nickel ammonium sulphate in 100 parts 
by weight of distilled water. If too acid, the solution is neutral- 
ized with spirits of sal ammoniac to a slightly acid reaction. The 
solution is prepared by boiling the salt with the corresponding 
quantity of water, using in summer 10 parts of nickel salt to 100 
of water, but in winter only 8 parts, to prevent the nickel salt 
from crystallizing out. This bath, which is frequently used, 
possesses however a considerable degree of resistance to conduc- 
tion, and hence requires a strong current for the deposition of 
the nickel. It also requires cast nickel anodes, since with the 
use of rolled anodes, nickeling proceeds in a very sluggish 
manner. However, the cast anodes rapidly render the bath 
alkaline, necessitating a frequent correction of the reaction. To 
decrease the resistance, recourse has been had to certain conducting 
salts, and below, the most common nickel baths will be discussed, 
together with their mode of preparation and action, as well as 
their availability for certain purposes. 

II. Nickel ammonium sulphate 17 ozs., ammonium sulphate, 
17 ozs., distilled water 10 quarts. 

Boil the salts with the water, and, if the solution is too acid, 
restore its neutrality by spirits of sal ammoniac ; then gradually 
add solution of citric acid until blue litmus paper is slowly but 
visibly reddened. The bath deposits rapidly, it possessing but 
little resistance; an electromotive force of 1.8 to 2 volts suffices, 
and all metals (zinc, lead, tin and Britannia after previous cop- 
pering) can be nickeled in this bath. However, upon rough 
castings and iron a pure white deposit is difficult to obtain, fre- 
quent scratch-brushing with a medium hard steel brush being 
required. On account of the great content of sulphate of am- 
monium in the bath, the nickel deposit piles up especially on the 
lower portions of the objects, which in consequence readily 
become dull (bmn or over-nickel, for which see later on), while 
the upper portions are not sufficiently nickeled. For this reason 
the objects must be frequently turned in the bath so that the lower 
portions come uppermost. This piling up of the deposit also 
frequently prevents a uniform thickness of the deposit. 

III. Nickel ammonium sulphate 25J ozs., ammonium sulphate 
8 ozs., crystallized citric acid If ozs., water 10 to 12 quarts. 



140 ELECTRO-DEPOSITION OF METALS. 

This bath is prepared in the same manner as the preceding, the 
salts being dissolved in boiling water, and ammonia added until 
blue litmus paper is only slightly reddened. 

This bath requires a somewhat greater electromotive force than 
the preceding, or about 2 to 2.2 volts. The formation of the nickel 
deposit is, however, more uniform, the nickeling of a beautiful 
white color, dense and hard, and consequently stands polishing 
without danger of the nickel grinding off, even if not very thickly 
plated. It is very suitable for nickeling ground surgical instru- 
ments, as well as all ground iron articles which are to be thickly 
and solidly plated, and for heavy, solid nickeling of copper, brass, 
bronze, etc. It is much used in this country, either with or with- 
out the addition of citric acid. 

If, after working for some time, the bath loses conducting 
power, the objects, with the use of the proper current, become 
blackish without a reduction of nickel being perceptible ; while 
with a stronger current the objects, to be sure, are nickeled white, 
but the deposit readily peels off. In this case the conducting 
power has to be increased by the addition of ammonium sulphate. 
The bath should always be kept so that it shows a slightly acid 
reaction It is best to use rolled anodes. 

IV. Nickel ammonium sulphate 23 ozs., ammonium chloride 
(crystallized) 11 J ozs., water 10 to 12 quarts. 

The bath is prepared in the same manner as given for II. 
and III. It nickels very rapidly and quite white, but the deposit 
is soft, and hence care must be had in polishing upon cloth or 
felt bobs, the corners and edges of the objects especially requiring 
careful handling. On account of the danger of peeling off, a 
heavy deposit of nickel cannot be obtained in this bath, since, in 
consequence of the rapid precipitation, the deposit condenses and 
absorbs hydrogen, is formed with a coarser structure, and turns 
out less uniform and dense. These phenomena are a hindrance 
to a heavy deposit, which, if it is to adhere, must be homogeneous 
and dense. As previously mentioned, baths with the addition of 
chlorides as well as those prepared with nickel chloride and nickel 
nitrate are not suitable for the solid nickeling of iron ; they are, 
however, well adapted to the rapid light nickeling of cheap 
articles. The tension required for this bath is 1 .8 volts. 



DEPOSITION OF NICKEL AND COBALT. 141 

V. Nickel chloride (crystallized) 1 7 J ozs., ammonium chloride 
(crystallized) 17 J ozs., water 12 to 15 quarts. 

The bath is prepared in the same manner as given for II. and 
III., though solution may be effected cold. The bath precipi- 
tates very readily and is especially liked for nickeling zinc cast- 
ings. Tension of current 1.5 to 1.75 volts. 

For nickeling iron this bath has the same disadvantages, and 
even to a still greater extent than the preceding. 

"VI. Baths containing boric acid. — Weston recommends the 
following composition of nickel baths : Nickel chloride 17 J ozs., 
boric acid 7 ozs., water 20 quarts, or, nickel ammonium sulphate 
35 ozs., boric acid 17 J ozs., water 25 to 30 quarts. Both solu- 
tions are said to be improved by adding caustic potash or caustic 
soda so long as the precipitate formed by the addition dissolves.* 

These compositions, however, cannot be recommended, chiefly 
because the baths work faultlessly for a comparatively short time 
only ; all kinds of disturbing phenomena make their appearance, 
the deposit being no longer white but blackish and the baths soon 
failing entirely. Kaselowsky's formula yields similar results. It 
is prepared by dissolving, with the assistance of heat, 35J ozs. of 
nickel ammonium sulphate and 17f ozs. of boric acid in 20 quarts 
of water. If an entirely neutral double sulphate has not been 
employed, this bath also generally fails after two or three months' 
use. By taking the ordinary nickel salt, which is crystallized 
from an acid solution and employing rolled nickel anodes, the 
bath will certainly have to be thrown away after using it at the 
utmost for three months. 

Such a bath, with boric acid, however, works satisfactorily by 
proceeding as follows : — 

VII. Nickel ammonium sulphate 21 ozs., chemically pure 
nickel carbonate If ozs., chemically pure crystallized boric acid 
10 \ ozs., water 10 to 12 quarts. 

Boil the nickel ammonium sulphate and the nickel carbonate 
in the water until the development of bubbles of carbonic acid 
ceases and blue litmus paper is no longer reddened ; then add 
the boric acid, and after allowing the whole to boil a few minutes 

* Dingler's Journal, 235, p. 404. Wagner's Jahresbericht, 1883, p. 146. 



142 ELECTRO-DEPOSITION OF METALS. 

longer, cool and filter. The reaction of the solution is strongly 
acid and must not be removed by alkaline additions. A bath 
thus prepared lasts at least twice as long as those which are pre- 
pared without previous neutralization of the double nickel salt 
by nickel carbonate. The treatment of the bath varies according 
to whether rolled or cast anodes are used ; in the first case free 
sulphuric acid readily forms, the consequence of which will be 
an exfoliating reduction of nickel with the simultaneous appear- 
ance of a strong evolution of hydrogen on the objects. The bath 
must then be compounded with an addition of alkali (except 
spirit of sal ammoniac) corresponding to the quantity of free sul- 
phuric acid. With the use of cast anodes the bath readily be- 
comes alkaline, and requires the restoration of the acid reaction, 
since a bath containing boric acid, which has become alkaline, 
also nickels gray-black and dull, even when the deposit has ac- 
quired only slight thickness. It is, therefore, best to work with 
mixed anodes, i. e., rolled and cast. 

A bath prepared according to the above formula requires an 
electromotive force of about 2.5 volts; while working, the resis- 
tance of the solution increases somewhat and reaches its maximum 
in 3 or 4 weeks when it remains constant. All baths prepared 
with an addition of boric acid exhibit the property of their resis- 
tance growing with comparative rapidity in the beginning, but 
not increasing after having reached a certain limit. 

In the following a few other formulae for nickel baths are given 
which may be advantageously used for certain purposes, but not 
for nickeling all kinds of metals. 

VIII. Nickel sulphate, 10 J ozs. ; potassium citrate, 7 ozs* ; 
ammonium chloride, 10 J ozs. ; water 10 to 12 quarts. 

To prepare the bath dissolve 10J ounces of nickel sulphate and 
3 \ ounces of pure crystallized citric acid in water ; neutralize accu- 
rately with caustic potash, and then add the ammonium chloride. 
This bath is especially adapted for the rapid nickeling of polished, 
slightly coppered zinc articles. The deposition is effected with a 
very feeble current, without the formation of black streaks, such 
as are otherwise apt to appear in nickeling with a weak current. 
The deposit itself is dull and somewhat gray, but acquires a very 
fine polish and pure white color by slight manipulation upon the 



DEPOSITION OF NICKEL AND COBALT. 143 

polishing disks. With a stronger current the bath is also suitable 
for the direct nickeling of zinc articles ; it must, however, be 
kept strictly neutral. The bath works with rolled anodes, and 
but seldom requires a correction of the reaction. 

IX. Nickel phosphate 8 J ozs., sodium pyrophosphate 26 J ozs., 
water 10 to 15 quarts. Dissolve the sodium pyrophosphate in 
water, heat the solution to about 167° F. and add the nickel phos- 
phate with constant stirring. Nickel phosphate is obtained as a 
pale green powder by precipitating solution of nickel sulphate 
with sodium phosphate. 

This bath yields a very fine dark nickeling upon iron, brass, 
copper, as well as directly, without previous coppering, upon sheet 
zinc and zinc castings, and may be advantageously used for deco- 
rative purposes where darker tones of nickel are demanded. 

X. A fairly good nickel-bath for electro-platers having but a 
feeble current at their disposal is obtained from a solution of nickel 
ammonium sulphate 22J ozs., magnesium sulphate 11 J ozs., water 
10 to 12 quarts. 

This bath precipitates readily and strongly and a heavy coating 
can also be deposited upon iron without fear of the disagreeable 
consequences of bath IV ; even zinc may be directly nickeled in 
it with a comparatively feeble current. The deposit, however, 
turns out rather soft, with a yellowish tinge and the bath does not 
remain constant, but fails after working at the utmost three or 
four months, the anodes being scarcely attacked 

In the following the composition of a few nickel baths is given 
which have recently been highly recommended : — 

XL Dissolve 35J ozs. of nickel sulphate, 25J ozs. of neutral 
ammonium tartrate and 77 grains of tannin in 20 quarts of water. 
This bath is said to yield a very white deposit of any thickness 
desired without danger of peeling off. For those who wish to 
try the bath it may be mentioned that the most suitable tension is 
3.5 volts. 

XII. An English formula is as follows: dissolve 17J ozs. of 
nickel sulphate, 9 J ozs. of tartaric acid and 2 J ozs. of caustic potash 
in 10 quarts of water. 

The addition of bisulphide of carbon to nickel baths which 
has recently been recommended by Bruce, is not advisable. Ac- 



144 ELECTRO-DEPOSITION OF METALS. 

cording to Bruce, such an addition prevents the nickel deposits 
from becoming dull when reaching a certain thickness, but re- 
peated experiments made strictly in accordance with the directions 
given, did not confirm this statement. 

In some works on galvanoplasty a solution of nickel cyanide in 
potassium cyanide is recommended for nickeling, but experiments 
failed to obtain a proper reduction of nickel. 

We would here add the general remark that freshly prepared 
nickel baths mostly work correctly from the beginning, though it 
may sometimes happen that the articles first nickeled come from 
the bath with a somewhat darker tone. In such case it is advis- 
able to suspend a few anodes to the cathode and allow the bath 
to work one or two hours when the nickeling will proceed fault- 
lessly. 

A few words may here be said in regard to what may be termed 
a nickel bath without nickel salt. It simply consists of a 15 to 20 
per cent, solution of ammonium chloride which transfers the nickel 
from the anodes to the articles ; cast anodes are almost exclusively 
used for the purpose and the depositions may be effected with 
quite a feeble current. Before the solution acquires the capacity 
of depositing, quite a strong current has to be conducted through 
the bath until the commencement of a proper reduction of nickel. 
This bath is only suitable for coloring very cheap articles, it not 
being possible to produce solid nickeling with it, and it is here 
mentioned because it may serve as a representative of a series of 
other galvanic baths in which the transfer of the metal is effected 
by sal ammoniac solution without the use of metallic salts, for 
instance, iron, zinc, cobalt, etc. 

Nickel anodes. — Either cast or rolled nickel plates are used as 
anodes, which must of course be as pure as it is possible to obtain 
them. Every impurity of the anodes passes into the bath and 
jeopardizes its successful working. If too thin, the anodes in- 
crease the resistance; for small baths rolled anodes 0.079 inch 
thick are generally used, and as a rule they should not be less 
than 0.039 inch thick. For larger baths it is better to use plates 
from 0.11 to 0.19 inch thick, while the thickness of cast anodes 
may vary between 0.11 and 0.39 inch according to the size of the 
bath and the purpose for which it is to be used. The use of 



DEPOSITION OF NICKEL AND COBALT. 145 

insoluble anodes of gas carbon or platinum, either by themselves 
or in conjunction with nickel anodes as frequently recommended, 
is not advisable. The harder and the less porous the nickel anode 
is, the less it is attacked in the bath and the less it fulfils the object 
of keeping constant the metallic content of the solution. On the 
other hand, the softer and the more porous the anode is, the more 
readily it dissolves, because it conducts the current better and 
presents more points of attack to the bath ; and the more it is 
dissolved, the more metal is conveyed to the bath. With the 
sole use of rolled anodes and working with a feeble current, free 
acid is formed in the bath ; on the other hand, by working with 
cast anodes alone, the bath readily becomes alkaline. Now it seems 
that the phenomenon of the possibility of a bath also becoming 
alkaline even with the sole use of rolled anodes, especially when 
working with a strong current, has led to the proposal of suspend- 
ing in the bath, besides the nickel anodes, a sufficient number of 
insoluble anodes in order to effect a constant neutrality of the 
bath. It would lead too far to go into the theory of the secondary 
decompositions which take place in a nickel bath, to prove that 
though neutrality is obtained, it can only be done at the expense 
of the metallic content of the bath. Hence, this impracticable 
proposal shall here be overthrown by practical reasons, it only 
requiring to be demonstrated that in baths becoming alkaline the 
content of nickel also decreases steadily though slowly. This fact 
in itself shows that in order to save the occasional slight labor of 
neutralizing the bath, the decrease of the metallic content should 
not be accelerated by the use of insoluble anodes. For larger baths 
the use of expensive platinum anodes as insoluble anodes need not 
be taken into consideration, because for large surfaces of objects 
correspondingly large surfaces of platinum anodes would have to 
be present, as otherwise the resistance of thin platinum sheets 
would be considerable. But such an expensive arrangement 
would be justifiable only if actual advantages were obtained, 
which is not the case, because though the platinum does abso- 
lutely not dissolve, the deficiency of metallic nickel in the bath 
caused by such anodes must be in some manner replaced. The 
insoluble anodes of gas carbon which have frequently been pro- 
posed are attacked by the bath ; particles of carbon becoming 
10 



146 ELECTRO-DEPOSITION OF METALS. 

constantly detached and floating upon the bath, deposit themselves 
upon the objects and cause the layer of nickel to peel off. Fur- 
thermore, by the use of nickel anodes in conjunction with carbon 
anodes, the current on account of the greater resistance of the 
latter, is forced to preferably take its course through the metallic 
anodes, in consequence of which the articles opposite the nickel 
anodes are more thickly nickeled than those under the influence 
of the carbon anodes. With larger objects this inequality in the 
thickness of the deposit is again a hindrance to obtaining layers 
of good and uniform thickness such as are required for solid 
nickeling. According to long practical experience, the best plan 
is to use foiled and cast anodes together in one bath. The pro- 
portion of cast to rolled anodes depends on the composition of 
the bath, but it may be laid down as a rule, that baths with 
greater resistance require more cast anodes, and baths with less 
resistance more rolled anodes. Cast anodes, to be sure, have the 
disadvantage of soon becoming spongy, and crumbling before 
being entirely used up. Furthermore, the surfaces of nickel 
anodes cast in iron moulds are so hard as to temporarily resist the 
action of the bath, while the interior dissolves only partially, since 
on the one hand the oxygen separating on the anode, which is 
necessary for solution, escapes partially unused, and on the other, 
the intact outer layer prevents the bath from coming in contact 
with the interior of the anode. 

The cast anodes suspended to the ends of the conducting rods 
are especially strongly attacked, and therefore, when rolled and 
cast anodes are used together, it is best to suspend the latter more 
towards the centre, and the first on the ends of the rods. 

These disadvantages, however, are not sufficient to prevent the 
use of a combination of cast and rolled anodes when required by 
the composition of the bath. The spongy remnants are thoroughly 
washed in hot water, dried and sold. 

The rolled nickel anodes are less liable to corrosion and may be 
used up to the thickness of a sheet of paper before they fall to 
pieces. It is, however, best to replace them by fresh anodes be- 
fore they become too thin, since with the decrease in thickness 
their resistance increases. 

The surface of the anodes suspended in the baths should be at 



DEPOSITION OF NICKEL AND COBALT. 147 

least as large as that of the articles to be nickeled ; it is however 
preferable that they should present twice or three times the sur- 
face, in order that the bath may be kept thoroughly saturated 
with nickel. 

It is best to allow the anodes to remain quietly in the bath, 
even when the latter is not in use, they being in this case not 
attacked. By frequently removing and replacing them they are 
subject to concussion, in consequence of which they crumble 
much more quickly than when remaining quietly in the bath. 

In the morning, before nickeling is commenced, the anodes will 
frequently show a reddish tinge, which is generally ascribed to a 
content of copper in the bath or the anodes. However, this 
reddish coloration also appears even when an analysis shows the 
anodes as well as the bath to be absolutely free from copper. It 
is very likely due to a small content of cobalt, from which nickel 
anodes can never be entirely freed. It would seem that by the 
action of a feeble current cobaltous hydrate is formed, which 
however immediately disappears on conducting a strong current 
through the bath. 

The anodes are supported by nickel wire 0.11 to 0.19 inch 
thick or by strips of nickel sheet riveted on. 

If after working for some time a nickel bath has become alka- 
line, which can be readily determined by a test with litmus paper, 
the neutrality or a slightly acid reaction can in a few minutes be 
restored by the addition of either citric, sulphuric, acetic or boric 
acid, according to the composition of the bath. On the other 
hand, when the bath contains too much free acid, it is removed 
by the addition of spirits of sal ammoniac, ammonium carbonate, 
potash, or by boiling with nickel carbonate, the choice of the 
remedy depending on the composition of the bath. 

The process of electro-nickeling. — Next to the correct composi- 
tion of the bath and the proper selection of the anodes, the 
success of the nickeling process depends on the thorough cleansing 
of the objects and the correct current-strength. 

The directions for the removal of grease, etc., given on p. 125, 
also apply to objects to be nickeled. In executing the manipula- 
tions, it should always be borne in mind that though dirty greasy 
parts become coated with nickel, the deposit immediately peels 



148 ELECTRO-DEPOSITION OF METALS. 

off by polishing, because an intimate union of the deposit with 
the basis-metal is only effected with perfectly clean surfaces. 
Touching the cleansed articles with the dry hand must be strictly 
avoided ; however, if large and heavy objects have to be handled, 
the hands should first be freed from grease by brushing with lime 
and rinsing in water, and be kept wet. 

As previously mentioned, the cleansed objects must not be 
exposed to the air, but immediately placed in the bath, or, if this 
is not practicable, be kept under clean water. 

While copper and its alloys (brass, bronze, tombac, German 
silver, etc.), as well as iron and steel, are directly nickeled, zinc, 
tin, Britannia, and lead are generally first coppered or brassed. 
With a suitable composition of the nickel bath and some experi- 
ence, the last-mentioned metals may also be directly nickeled, 
but, as a rule, previous coppering or brassing is preferable, the 
certainty and beauty of the results being thereby considerably 
increased. 

Many operators prefer coppering or brassing steel and iron 
articles before nickeling, and claim that by doing so better pro- 
tection against rust is secured. While experiments have shown 
that with the thin coat of copper or brass generally applied, this 
claim is scarcely tenable, the previous coppering of iron objects 
has the advantage that, in case they have not been thoroughly 
cleansed, the deposit of nickel is less liable to peel off, the alka- 
line copper bath completing the removal of grease, but with 
objects carefully cleansed according to the directions given on 
p. 125, previous coppering is not necessary. 

The objects should never be suspended in the bath without current; 
the baths, with few exceptions, exerting a chemical action upon 
many metals, which is injurious to the electro-plating process, and 
especially with the nickel bath is it necessary to connect the anode- 
rods and object-rods before suspending the articles in the bath. 

The suitable current strength has already been fully discussed 
on p. 79 (" Electro-plating Arrangements in Particular"), and with 
reference to that section we may here be comparatively brief. 

It has there already been said that the surfaces of objects to be 
nickeled must be in due proportion to the effective zinc-surface 
of the battery if the latter be used for generating the current ; 



DEPOSITION OF NICKEL AND COBALT. 149 

further, the surface of anodes suspended in the bath must be at 
least equal to that of the objects, though in most cases it is better 
that it should be larger. On p. 79 it has also been explained 
how, according to existing circumstances, the elements have to be 
coupled to a battery in order to be sure of success. Two Bunsen 
elements, coupled one after the other, yield for nearly all nickel- 
baths the electro-motive force required for the reduction of the 
nickel ; for baths with great resistance it will, however, be better, 
especially when the filling of the elements is no longer fresh, to 
couple three elements one after the other, and to neutralize a 
momentary excess of current by the resistance board. 

An error is frequently committed in nickeling with too strong 
a current, the consequence being that the deposit on the lower 
portions of the objects soon becomes dull and gray-black, while 
the upper portions are not sufficiently nickeled. This phenome- 
non, which is due to the reduction of the nickel with a coarse 
grain in consequence of too powerful a current, is called burning 
or over-nickeling. A further consequence of nickeling with too 
strong a current is that the deposit readily peels off after it reaches 
a certain thickness. This phenomenon is due to the hydrogen 
being condensed and retained by the deposit, which prevents thick 
depositions. 

Especially do those objects suspended on the ends of the rods 
nickel with great ease ; this evil can be avoided by hanging on both 
ends of the rods a strip of copper-sheet about 0.39 inch wide, and 
of a length corresponding to the depth of the bath. 

The following criteria may serve for judging whether the nick- 
eling progresses with a correct current : In two or at the utmost 
three minutes all portions of the objects must be perceptibly 
coated with nickel, however, without a violent evolution of gas 
on the objects ; small gas bubbles rising without violence and 
with a certain regularity are an indication of the operation pro- 
gressing regularly. If, after two to three minutes, the objects 
show no deposit the current is too weak, and in most cases the 
objects will have acquired dark, discolored tones. In such case 
either a stronger current must be introduced by means of the 
resistance board, or if the entire volume of current generated 
already passes into the bath, the object-surface has to be dimin- 



150 ELECTRO-DEPOSITION OF METALS. 

ished, or, if this is not desired, the battery must be strengthened 
by adding more elements, or by fresh filling, etc. 

If, on the other hand, a violent evolution of gas appears on 
the objects, and the latter are well covered in a few seconds, and 
the at first white and lustrous nickeling changes in a few minutes 
to a dull gray, the current is too strong, and must be weakened 
either by the resistance board, or uncoupling a few elements, or 
diminishing the anode-surface, or finally by suspending more 
objects in the bath. 

The density of current most suitable for nickeling copper, 
copper-alloys, iron, and steel varies between 0.4 and 0.8 ampere 
per 15.5 square inches, while zinc, after previous coppering, 
requires 1.3 to 1.5 amperes. 

It is in all respects advisable first to cover the objects with the 
use of a strong current, i. e., to give the first deposit rapidly in 
order to withdraw the metals from the action of the bath, and 
then finish the operation after reducing the current to the suitable 
strength. With a current thus regulated the objects may be 
allowed to remain in the bath for hours and even for days. It is 
further possible to nickel by weight and attain depositions of 
considerable thickness. 

If very thick deposits of nickel are desired, the objects must be 
frequently turned in the bath, as the lower portions nickel stronger 
than the upper ; further, as soon as the deposit acquires a dull 
bluish lustre, it has to be thoroughly scratch-brushed, in doing 
which, the objects must, however, not be allowed to become dry. 
After scratch-brushing it is advisable to cleanse the deposit once 
more with the lime-brush, and after rinsing replace the objects in 
the bath. If burnt places cannot be brightened and smoothed 
with the scratch-brush, the desired object is readily attained with 
the assistance of emery paper or pumice. 

For solid nickeling it suffices in most cases to allow the objects 
to remain in the bath until the dull bluish lustre appears ; this 
being an indication that the deposit has acquired considerable 
thickness, and does not take a further regular deposit. If such 
objects are permitted to remain longer in the bath without scratch- 
brushing, the dull bluish tone soon passes into a dull gray, and 



DEPOSITION OF NICKEL AND COBALT. 151 

all the metal deposited in this form must be polished away in 
order to obtain a bright lustre. 

Whether the deposit of nickel is sufficiently heavy for all 
ordinary demands is, according to Fontaine, shown by rubbing a 
nickeled corner or edge of the object rapidly and with energetic 
pressure upon a piece of planed soft wood until it becomes hot. 
The nickeling should bear this friction. 

If the objects after having for some time been suspended in the 
bath are only partially nickeled, it is very likely due to the defec- 
tive arrangement of the anodes. This occurs chiefly with large 
round objects, further with articles having deep depressions (cups, 
vases, etc.). 

For flat objects it is sufficient to suspend them between two 
rows of anodes ; round objects with a larger diameter should be 
quite surrounded with anodes, and be as nearly as possible equi- 
distant from them. This arrangement should especially not be 
neglected where a heavy and uniform deposit of nickel is to be 
given to round or half-round surfaces — for instance, large half- 
round stereotype plates for revolving presses. 

While for smooth articles the most suitable distance of the 
anodes from the objects is 3} to 5f inches, for objects with de- 
pressions and hollows it must be larger, if it is not preferred to 
make use of the methods described later on. However, a deposit 
of a uniform thickness cannot be obtained by this means, because 
the portions closer to the anodes will acquire a thicker deposit 
than the hollows ; hence the use of a small hand-anode, which is 
connected by means of a thin flexible wire with the anode-rod ? 
and introduced into the depressions and hollows, is to be pre- 
ferred. This, of course, renders it necessary for a workman to 
stand alongside the bath and execute the operation by hand ; but 
as the small anode can be brought within a few millimetres of the 
surface of the article, and at this distance slowly moved around 
it, a correspondingly thick deposit is in a short time formed. 

In nickeling lamp-feet of cast zinc this operation can scarcely 
be avoided, especially if the depressed portions are also to have a 
uniformly good deposit. 

Besides the above-mentioned rules for nickeling, which are also 



152 ELECTRO-DEPOSITION OF METALS. 

valid for other electro-plating processes, the following may be 
given : — 

In suspending the objects in the bath rub the metallic hooks or 
wires, with which they are secured to the rods, a few times to and 
fro upon the rod, in order to be sure that the place of contact is 
purely metallic. It is also well to acquire the habit of striking 
the rod a gentle blow with the finger every time when suspending 
an object, the gas-bubbles settling on the articles becoming thereby 
detached and rising to the surface. It is further advisable before 
securing the objects to the object-rod several times to move them 
up and down, so to say, shake them beneath the fluid, whereby, 
on the one hand, the layers poorer in metal are mixed with those 
richer in metal, and on the other, any dust which may float upon 
the bath and settle on the objects is removed. 

The objects suspended in the bath should not touch one another, 
nor one surface cover another, and thus withdraw it from the 
direct action of the anode. In the first case stains will readily 
form on the places of contact, and in the latter the covered surface 
acquires only a slight deposit. That the objects must not touch 
the anodes need scarcely be mentioned. 

Objects with depressions and hollows should be suspended 
in the bath so that the air in the hollows can escape, which is 
effected by turning the depressions upward, or if there are several 
depressions on opposite sides, by turning the articles about after 
being introduced into the bath. Air bubbles remaining in the 
hollows prevent contact with the solution, no deposit being formed 
on such places. 

It remains to say a few words in regard to the so-called pola- 
rizing phenomena. In the theoretical part, it has been shown 
that by dipping two plates of different metals in a fluid, a counter 
or polarizing current is generated, which is the stronger, the further 
the two metals are removed from one another in the series of ten- 
sion, and the more they differ in their electrical behavior. If the 
anodes in a nickel bath are of nickel and the articles of copper, 
the counter-current will be slight, because copper and nickel 
stand together in the series of tension (p. 28). The counter- 
current however becomes greater, when iron objects are hung 
in the bath, and greatest with zinc surfaces which are to be 



DEPOSITION OF NICKEL AND COBALT. 153 

nickeled, because zinc being the most electro-positive metal, 
differs widely in its behavior from nickel. Now, since the 
counter-current flows in a direction opposite to that of the 
current introduced in the bath, the latter is weakened, and the 
more so, the stronger the counter-current is. This explains why 
iron requires a stronger current for nickeling than copper alloys, 
and zinc a stronger one than iron. 

Now it may happen that the counter-current becomes so strong 
as to entirely annul the effect of the principal current, and even 
to reverse the latter, the consequence being that, in the first case, 
the formation of the deposit is interrupted, and in the latter, that 
the deposit is again destroyed, and the metals of which the articles 
consist dissolve and contaminate and spoil the bath. To avoid 
this, a main current must be conducted into the bath, which, by 
its sufficiently large electro-motive force, can overcome the 
counter-current, and the consequences of the reversion of the 
current can be prevented by using the galvanometer and observ- 
ing the deflection of its needle which (according to p. 86), in 
proper time indicates the appearance of a reversed current. Now 
if a nickel plater has only a slight current at his disposal, it fol- 
lows from the above explanation, that before nickeling the more 
electro-positive metals, such as iron, tin, zinc, it is best to first 
copper them and thereby annul the action of these metallic sur- 
faces as regards the formation of the counter-current. 

It happens comparatively seldom that the counter-current 
becomes so strong as to destroy the deposits formed, because for 
nickeling, powerful Bunsen elements with two acids or dynamo- 
electric machines with at least 4 volts' tension are generally used ; 
it is however well to acquaint the operator with all possible con- 
tingencies, and to explain the reason why the articles are prefera- 
bly covered with a strong current. Sprague recommends an 
initial current of 5 volts' tension, but in most cases one of 3.5 
volts suffices for nickeling iron and copper alloys. 

Nickeling en masse of small and cheap objects. — This is effected 
by stringing the objects, if feasible, upon a copper- wire, and 
placing a large glass-bead between every two objects to prevent 
the surfaces from sticking together in the bath. Such objects 
being generally only slightly nickeled, it suffices to allow them 



154 



ELECTRO-DEPOSITION OF METALS. 



to remain for a few minutes, only, in the bath with a strong cur- 
rent, it being advisable to diligently shake the bundles in order 
to effect a change of position of the objects and prevent their 
touching one another, notwithstanding the glass-bead placed 
between them. 

Very small objects which cannot be strung upon wire are 
nickeled in sieves. To the bottom of a stoneware sieve is secured 
a copper or brass wire, which is connected with the object-rod, and 
then the objects are placed in the sieve. Since nickel baths, as a 
rule, do not conduct sufficiently well to nickel the objects in the 
sieve, which must be constantly shaken, it is advisable to hold 
with one hand an anode connected by a flexible wire with the 
anode-rod in the sieve, while the other holds the sieve (Fig. 72) 

Fig. 72. 




and constantly shakes and turns it. For nickeling in sieves, it is 
further advisable to heat the nickel bath. 

Warren has recently described a solution of nickel and one of 
cobalt, which can be decomposed in a simple cell apparatus. 
With the nickel solution, which was prepared by dissolving 100 
parts by weight of nickel chloride in as little water as possible 
and mixing with a concentrated solution of 500 parts of Rochelle 
salt, no satisfactory results could be obtained ; the cobalt solution 



DEPOSITION OF NICKEL AND COBALT. 155 

however yielded good results, and would seem to be suitable for 
electro-plating small objects en masse. It will be further dis- 
cussed under " Cobalting." 

Defective nickeling has first to be removed before the objects can 
be re-nickeled, since nickel will not adhere to a coating of the 
same metal. For stripping the old coating Watt and Elmore 
recommend the following acid mixture : Sulphuric acid of 66° 
B. 16 lbs., nitric acid 4 lbs., water 2 quarts. Add the sulphuric 
acid to the water gradually, and when the mixture has cooled 
down add the nitric acid and stir with a glass rod. When cold 
it is ready for use. The objects to be stripped should be attached 
to a piece of stout brass or copper wire and placed in the stripping 
liquid. The operation of stripping should be conducted in the 
open air, or in a fire-place with good draught so that the acid 
fumes may escape through the chimney. From the moment the 
objects are immersed in the stripping bath, they should be care- 
fully watched, being frequently raised out of the bath to see how 
the operation progresses, and they should not be allowed to remain 
in the liquid one moment after the nickel has been dissolved from 
the surface. When the stripping of brass or copper work has 
been properly conducted the surface of the stripped object presents 
a smooth and bright surface, but little affected by the acid bath. 

Mechanically the old nickeling is removed by brushing with 
emery. From depressions as much as possible is removed with 
the brush, after which the object is freed from grease and pickled 
and coppered before nickeling. In this case the layer of copper 
serves as a cement for the old and new deposit, and there will be 
no danger of the new deposit peeling off in polishing. 

It has also been proposed to remove the nickel from the articles 
by means of the battery or dynamo machine by making them the 
anodes in a nickel bath ; but in this case a separate solution should 
be employed for the purpose. 

As a remedy against the yellowish tone of the nickeling, Pfan- 
hauser recommends suspending the nickeled articles immediately 
after taking them from the nickel bath, as anodes in a nickel bath 
acidulated with citric or hydrochloric acid, a piece of sheet nickel 
serving as cathode, and to allow the current to act for a few 
seconds. It is claimed that thereby the basic nickel salts sepa- 



156 ELECTRO-DEPOSITION OF METALS. 

rated together with the nickel, and to which according to Pfan- 
hauser, the yellowish tinge is due, are dissolved and the nickeling 
will show a pure white tone. 

In the following a compilation of the principal phenomena 
which may occur in nickeling is briefly given as well as the means 
of avoiding them : 1. The articles do not become coated with 
nickel, but acquire discolored, generally darker tones. Reasons : 
The current is either too feeble to effect the reduction of nickel, 
and the coloration is in consequence of the chemical action of the 
nickel solution upon the metals constituting the objects. Remedy : 
Increase the current or diminish the area of suspended objects ; 
also examine whether the current actually passes into the bath, 
otherwise clean the places of contact. 

2. A deposition of nickel takes place, but it is dark or spotted 
or marbled, even with a sufficiently strong current. Reasons: 
The bath is either alkaline, which has to be ascertained by litmus 
paper, and, if so, the slightly acid reaction of the bath has to be 
restored by the addition of a suitable acid ; or, the bath is too 
concentrated, in which case a separation of crystals will be ob- 
served. This is remedied by diluting with water ; or, the nickel 
solution is very poor in metal, which can be remedied by the ad- 
dition of nickel salt ; it should also be tested as to the admixture 
of copper, the production of dark tones being frequently due to 
this. In this case the bath is allowed to work for some time, and 
if the content of copper is inconsiderable a white deposit will 
soon be obtained ; or the cleaning and pickling of the articles have 
been incomplete, which are remedied by again thoroughly cleaning 
them ; or the conducting power of the bath is insufficient, which 
is remedied by the addition of a suitable conducting salt. 

When freshly prepared baths yield dark nickeling, it can gen- 
erally be remedied by working the bath two or three hours. 

3. A yellowish tinge of the nickeling. Reasons: See under 
2 ; or, with cast iron an insufficient metallic surface which is 
remedied by repeating the scratch-brushing ; or, unsuitable com- 
position of the bath. 

4. The objects rapidly acquire a white deposit of nickel, but 
the color soon changes to dull gray-black, especially on the lower 
edges and corners. Reason: Too strong a current. Remedies: 



DEPOSITION OF NICKEL AND COBALT. 157 

Regulating the current or hanging in more objects, or uncoupling 
elements. Frequent turning of the articles. 

5. The nickeling is white, but readily peels off by scratching 
with the finger-nail or by the action of the polishing disk. 
Reasons : The current is too strong, which is remedied as under 
4 ; or, the bath is too acid. This is remedied by the addition 
of spirit of sal ammoniac, potassium carbonate, or nickel carbo- 
nate, according to the composition of the bath ; or, insufficient 
cleaning and pickling, which is remedied by the thorough clean- 
ing after removing the unsuccessful deposit, and if it cannot be 
entirely removed, coppering. 

6. Though nickeling may proceed in a regular manner, some 
places remain free from deposit. Reasons : Either some of the 
surfaces of the objects touch one another, or air bubbles are in- 
closed in cavities; or faulty arrangement of the anodes. Remedy: 
Removal of the causes. 

7. The deposit appears with small holes. Reasons : A deposit 
of particles of dust upon the objects. Remedy: Remove the dust 
from the surface. When there is a general turbidity of the bath 
in consequence of alkalinity, add the most suitable acid, and boil 
and filter the bath • or, insufficient removal of gas bubbles from 
the objects. Remedy : Shake the object-rods by blows with the 
finger. 

8. Deposition takes place promptly upon the portions of the 
objects next to the anodes, while deeper portions remain free from 
nickel or become black; or the portions covered by the suspending 
wire show dark lines. Reasons: Insufficient conducting power of 
the bath. With large depressions this cannot be remedied by the 
addition of a suitable conducting salt, but requires treatment with 
the hand-anode. 

Refreshing nickel baths. — According to their composition, the 
amount of work performed, and the anodes used, the baths will 
in a shorter or longer time require certain additions in order to 
keep their action constant. By " refreshing' ' is not understood 
the small edition of acid or alkali from time to time required for 
restoring the original reaction of the baths, but additions intended 
to increase the metallic content and diminished conductivity. 

The metallic content is increased by boiling the bath with some 



158 ELECTRO-DEPOSITION OF METALS. 

of the nickel salt used in its preparation, while the conductivity 
is improved by, at the same time, adding so much conducting salt 
as is necessary to restore the tension originally required for nickel- 
ing. Nothing definite can, of course, be said in regard to the 
quantity of such additions, it being advisable to observe their 
effect on a small portion of the bath, so as to be sure not to spoil 
the entire bath. 

Nickel baths bear, as a rule, refreshing several times, but as in 
the course of time they take up impurities, even when the greatest 
care is exercised, it is best to refresh them, at the utmost twice, 
and then to renew them entirely. 

Nickel deposits are polished upon felt disks or bobs of cloth, 
muslin, or flannel, with the use of Vienna lime, rouge, etc. (See 
"Polishing," page 112.) Sharp edges, corners, and raised por- 
tions should be held only with slight pressure against the polish- 
ing disks, they being more strongly attacked by them than flat 
surfaces. Knife blades and surgical instruments, with sharp 
edges, require special care in polishing, which will be referred to 
later on. 

After polishing, the nickeled objects, especially those with de- 
pressions, have to be freed from polishing dirt by brushing with 
hot soap water or hot caustic lye, then rinsed in hot water and 
dried in clean, fine sawdust. 

Objects which are not required to be polished, but left dead, 
that is, just as they come out of the nickel bath, should be taken 
from the bath one at a time, and at once plunged into perfectly 
clean hot water for a few moments, and then placed aside to dry 
spontaneously. Dead nickel being very readily stained or soiled, 
even when touched with clean hands, the work should be handled 
as little as possible. 

Nickeling sheet zinc. — The nickling of sheet-zinc has been sur- 
rounded with a great deal of mystery by those engaged in the 
manufacture, which may, perhaps, be excusable on the ground 
that there is scarcely another branch of the electro-plating indus- 
try in which experience had to be acquired at the sacrifice of so 
much money and time as in this. Nevertheless the nickeling of 
sheet-zinc makes no greater demand on the intelligence of the 
operator than any other electro-plating process, it requiring only 



DEPOSITION OF NICKEL AND COBALT. 159 

an accurate consideration of the relations of the electric behavior 
of zinc towards nickel ; consequently, a knowledge of the strength 
of the counter-current and of the chemical behavior of zinc to- 
wards the nickel solution, which may readily dissolve the zinc. 
Further, a correct estimation of the current-intensity required for 
a -determined zinc surface, as well as of the proper anode-surface, 
and the most suitable composition and treatment of the nickel 
baths. 

With due observation of these relations, the nickeling of sheet- 
zinc is accomplished as readily and faultlessly as that of other 
metals ; and the proposals to first cover the sheets in a bath with 
a strong current, and finish nickeling with a weaker current, or to 
amalgamate the zinc before nickeling, need not be considered. 

In the following the required conditions and the execution of 
nickeling sheet -zinc, together with the preliminary and final polish- 
ing of the sheets, will be fully described. 

The preliminary grinding or polishing is effected upon broad 
cloth disks (buffs) formed of separate pieces of cloth. The polish- 
ing lathes run with their points in movable bearings secured in a 
hanging cast-iron frame by a set screw and safety keys, or pre- 
ferably as shown in Fig. 67, p. 113, since with this construction 
an injury to the grinder by the lathe jumping out is impossible. 

The buffs, when new, have on an average a diameter of 12 to 
16 inches, and a width of 5f to 8 inches; the principal point in 
the construction of these bobs is uniform weight on all sides, the 
quiet running and the possibility of a good polish without great 
exertion depending on this. Bobs not well balanced run unsteadily 
and jump, thereby producing fine scratches upon the sheet. The 
bobs are constructed as follows : A square piece of cloth is folded 
fourfold and the closed point cut off with a pair of scissors so 
that on unfolding the cloth the hole produced by the cut is exactly 
in the centre of the cloth disk ; according to the diameter of the 
spindle more or less is cut away, but in every case just sufficient 
that the piece of cloth can be conveniently pushed upon the 
spindle. The latter, which is provided with a pulley and a hoop 
against which the pieces of cloth fix themselves as well as with a 
nut and screw for securing them, is vertically fastened in a vise, and 




160 ELECTRO-DEPOSITION OF METALS. 

the separate pieces of cloth are pushed upon it so that the second 
piece placed in position forms an angle of about 30° (Fig. 73), 
with the first, the operation being thus con- 
Fig- 73. tinued until the bob has the desired width. 
Next a small, but very strong iron disk is 
laid upon the cloth disk, and the separate 
pieces are pressed together as firmly as pos- 
sible with the screw. The spindle is then 
placed in the bearings, and after adjusting 
the belt upon the pulley the bob is revolved, 
a sharp knife being held against it to re- 
move the projecting corners. In polishing 
sheet zinc the bobs make 2400 to 3000 revolutions per minute, 
according to whether finely rolled or rougher sheets are to be 
polished. 

For the purpose of polishing or grinding, the operator places 
the sheet upon a support of hard wood of the same size and form 
as the sheet, and grasps the two corners of the sheet, nearest to his 
body, together with the support with the hands, applying with 
the balls of the hands the necessary pressure to hold the sheet 
upon the support. The lower half of the sheet, that furthest 
from the body, rests upon the knees of the operator and with them 
he presses the sheet against the polishing disk, constantly moving 
at the same time and at not too slow a rate, the knees from the right 
to the left, then from the left to the right and so on. Previous to 
polishing a streak of oil about 2 inches wide is applied by means 
of a brush to the centre of the sheet in the visual line of the 
operator, and the revolving bob is impregnated with Vienna 
lime by holding a large piece of it against it, when polishing 
of the lower portion of the sheet begins. When about § of 
the surface has thus been polished, the sheet is turned round and 
the remaining portion subjected to the same process. The sheet 
is then closely inspected to see whether there are still dirty or 
dull places, and if such be the case, it is polished once more after 
moistening it with some oil and again impregnating the bob with 
Vienna lime. The sheet being sufficiently polished the oil and 
polishing dirt are removed by dry polishing, after providing the 



DEPOSITION OF NICKEL AND COBALT. 



161 



bob with sufficient Vienna lime, so that the sheets when finished 
show no streaks of dirt or oil. 

Self-acting sheet polishing machines have been constructed by 
Dr. Sackur, F. Rauber, Eliackoff, and others. Such machines 
give a very good polish, but have the disadvantage that thin sheets, 
when polished upon them, become wrinkled or wind up on the 
polishing roller. 

In order to explain the principle upon which these machines 
are constructed, a description of F. Rauber's sheet grinding and 
polishing machine is given. With this machine metallic sheets of 
any length can be polished ; by the simultaneous lateral and longi- 
tudinal motion of the sheet a faultless polish is obtained, streaks 
and scratches being especially avoided. 

The machine essentially consists of the gearing A, and the 
actual polishing machine B, Figs. 74, 75, 76. The gearing A 
consists of the two standards a a, the shaft b, a fast and loose 
pulley, c c, the large driving wheel d, sl small driving wheel e, and 
the eccentric/. 



Fig. 74. 




The polishing machine B consists of the wooden frame g with 
wooden plate A, the two standards i i, the polishing roller k, the 
iron counter-roller /, the expanding contrivance m, which is 
effected by means of three spiral springs, the gearing n with the 
rope-drum o, the rope with the tongs g, and the shaking arrange- 
ment x. 
11 



162 



ELECTEO-DEPOSITION OF METALS. 




The machine is set in motion by the engaging coupling x on 
the gearing A. The shaft of the gearing makes about 200 revo- 
lutions per minute, and the polishing roller k is revolved by a 
belt from the driving-wheel d. At the same time the gearing n 
is set in motion by a belt from the driving-wheel e, in consequence 



DEPOSITION OF NICKEL AND COBALT. 163 

of which the rope is Avound upon the drum o, and the tongs on 
the rope draw the sheet to be polished under the polishing roller. 
If the sheet is to go back, the rope-drum o is disengaged by 
means of the coupling y, and the polishing roller k, which moves 
lightly upon the counter-roller I draws the sheet back. To pre- 
vent the sheet from jumping back the brake r is provided on the 
rope-drum o. By the treadle r v the workman is enabled to trans- 
port the sheet slowly or rapidly, as may be required. To move 
the sheet forward the rope-drum o is again engaged. The lateral 
motion of the sheet is effected by the shaking contrivance x. 

From the eccentric /, of the gearing A, the slide rod t is con- 
nected with the joint lever x and the latter by the pin s with the 
table plate h, whereby the latter when the machine is running is 
moved to the sides. 

The centre of motion of the table plate is upon the pin v. To 
regulate the pressure of the sheet against the polishing roller the 
expanding arrangement m is placed under the table plate h. It 
consists of three vertical bolts with spiral springs, each of which 
can be screwed up and down by a nut. 

To facilitate the lateral motion of the table plate h, the bolts of 
the expanding contrivance m are provided with rolls which press 
against the plate. If the tension is sufficient and a sheet is to be 
introduced, it is only necessary to draw the table plate down by 
means of the treadle to, to push the sheet under the polishing roll 
k and to engage the tongs g. In front of the gearing A is a table 
for the reception of the sheet, as shown in the illustration. 

The sheets are best freed from grease in two operations, first 
dry and then wet. For the dry process use a very soft piece of 
cloth and after dipping it in Vienna lime very finely pulverized and 
passed through a hair sieve, rub over the sheet in the direction at 
a right angle to the polishing streaks, applying a very gentle pres- 
sure. For the wet process dip a wet piece of cloth or a soft sponge 
free from sand into a paste of impalpable Vienna lime, whiting 
and water, and go carefully over the sheet so that no place remains 
untouched. Then rinse the sheet under a powerful jet of water, 
best under a rose, being especially careful to remove all the lime 
going over the sheet, if necessary, with a soft wet rag and observ- 
ing whether all portions appear evenly moistened. If such be 



164 ELECTRO-DEPOSITION OF METALS. 

the case, the cleaning is complete, otherwise the sheet has to be 
treated once more with lime. 

If the sheets are to be nickeled on one side only, two of them 
are placed together with their unpolished sides and fastened on the 
two upper corners with binding-screws to which is soldered a 
copper strip about 0.39 inch wide, by which they are suspended 
to the conducting rods. Plating is then at once proceeded with 
without allowing the sheets to remain exposed to the air longer 
than is absolutely necessary. Special care must be had that the 
lime does not dry, as this would produce stains. 

Some manufacturers nickel the cleansed sheets without previous 
coppering or brassing, and claim special advantages for such direct 
nickeling. This may be done with a bath of nickel sulphate and 
potassium citrate without or with a greater or smaller addition of 
sal ammoniac according to the area to be nickeled, and the inten- 
sity of current at disposal. However, sheet-zinc directly nickeled 
shows not the warm full tone of sheets previously coppered or 
brassed ; besides, direct nickeling requires a far more powerful 
current, so that it is not even more economical. 

For the nickeling process itself, it is indifferent whether the 
sheets are previously coppered or brassed, but the choice between 
the two is controlled by a few phenomena which must be men- 
tioned. The nickel deposit upon brassed sheets shows a decidedly 
whiter tone than that upon coppered sheets, and brassing would 
deserve the preference if this process did not require extraordinarily 
great care in the proper treatment of the bath, the nickel deposit 
readily peeling off generally in the bath itself, which never or only 
seldom occurs with coppered sheet, and then may generally be con- 
sidered due to insufficient cleaning or other defective manipula- 
tion. 

This peeling off of the nickel deposit may be prevented by 
giving due consideration to the conditions, and avoiding, on the 
one hand, too large an excess of potassium cyanide in the brass 
bath, and, on the other, by regulating the current so that no pale 
yellow or greenish brass is precipitated. Since nickeling with a 
strong current requires only a few minutes for a deposit of suffi- 
cient thickness capable of bearing polishing, it is generally desired 
to brass the sheets at the same time, so that the operation may 



DEPOSITION OF NICKEL AND COBALT. 165 

proceed rapidly and continuously. To do this, a very powerful 
current has to be conducted into the brass bath, the result being 
that a deposit with a larger content of zinc and a correspond- 
ingly lighter color is formed, but also with a coarser, less adherent 
structure, and this is the principal reason why the nickel deposit, 
together with the brass deposit, peels off. To avoid this, the brass- 
ing must be done with a current so regulated that the deposit 
separates uniformly, adheres firmly, and is not porous, the correct 
progress of the operation being recognized by the color being more 
like tombac, and not pale yellow or greenish. Where brassing 
has to be done quickly the content of copper in the brass bath 
must be increased to such an extent that a powerful current pro- 
duces a deposit of the above-mentioned color, and, hence, too large 
an excess of potassium cyanide must be strictly avoided. 

It will be seen that the brassing requires a certain attention 
which is not necessary in coppering, and therefore the latter is to 
be preferred. 

For coppering one of the baths III or V given under "Cop- 
pering," serves to which, for this special purpose, some more potas- 
sium cyanide may be added. The sheets should remain in this 
bath no longer than required to uniformly coat them with a 
beautiful red layer of copper, and under no circumstances must 
they be allowed to remain until the coppering commences to be- 
come dull or even discolored ; and they should come from the bath 
with a full or at least half lustre. When taken from the copper 
bath the sheets are thoroughly rinsed in a large water reservoir, 
the contents of which must be frequently renewed, care being 
had to remove any copper solution adhering to the unpolished 
sides which are not to be nickeled, since that would soon spoil 
the nickel bath. The sheets are then immediately brought into 
the nickel bath, it being best to suspend two, three, or four plates 
at the same time to prevent one from being more thickly nickeled 
than the other, and take them out the same way. In suspending 
the plates in the bath care should be had to bring them as soon 
as possible in contact with the conducting rod, a neglect of this 
rule being apt to produce blackish streaks and stains. 

Every separate nickel bath in which sheets are to be nickeled 
must be fed with the full current of a dynamo-machine, one of 



J 6(5 ELECTRO-DEPOSITION OF METALS. 

250 to 300 amperes with 4 volts' tension being generally used. 
According to the number of sheets, generally 6 to 8, each 20 x 20 
inches, to be nickeled, the dimensions of the vats are as follows : 
63 inches long, 15f inches wide, and 25 J inches deep, or, 83 
inches long, 15| inches wide, and 25 J inches deep. One to two 
minutes suffice to give 6 sheets a sufficiently thick deposit of 
nickel with a dynamo-machine of the above-mentioned capacity, 
and 2 to 3 minutes for eight sheets, and it may be accepted as a 
rule that with a bath of good conductivity, a density of current 
of from 1.4 to 1.5 amperes and 5 volts' tension is required per 
15.5 square inches of zinc surface for the solid nickeling of the 
sheets. For nickeling zinc in baths conducting with difficulty, 
for instance, a simple solution of sulphate of nickel and ammonia 
without the addition of conducting salts, or in baths containing 
boric acid, 1.3 to 1.4 amperes and 6 to 7 volts must be allowed 
per 15.5 square inches of zinc surface if the nickeling is to be 
effected in the above-named space of time. A density of current 
of 1.4 to 1.5 amperes and 4 to 4J volts, at which the sheets have 
to remain in the bath for 3 minutes, is the most suitable, the de- 
posit thus obtained being faultless in every respect, provided the 
nickel bath is of the proper composition. 

For nickeling sheet-zinc rolled anodes are, as a rule, only used, 
except when working with baths containing boric acid. The 
anode-surface must at least be equal to that of the zinc surface ; 
the distance between the anodes and the sheets should be from 3 
to 3f inches, and when the current-strength is somewhat scant 
the distance may be reduced to 2J inches. The nickel anodes 
have to be once daily taken from the bath and scoured bright 
with scratch-brushes and sand ; for the rest, all the rules given for 
nickel anodes are valid. 

Baths used for nickeling sheet-zinc soon become alkaline in 
consequence of the powerful current used, which is shown by red 
litmus paper turning blue; the alkalinity also manifests itself by 
the bath becoming turbid and the nickeling not turning out a 
pure white. The slightly acid reaction is restored by citric acid 
solution. The appearance of the dreaded black streaks and stains 
is due either to the current itself being too weak or to it having 
been weakened by an extremely great resistance of the nickel 



DEPOSITION OF NICKEL AND COBALT. 167 

bath ; also to an insufficient metallic surface of the anodes, which 
may either be too small or not sufficiently metallic on account of 
tarnishing ; and finally to an excessive alkalinity of the bath or 
insufficient contact of the hooks with the conducting rods. 

The metallic content of the bath must from time to time be 
augmented by the addition of nickel-salt, and the bath be, at 
certain intervals, filtered. When the conductivity abates it has to 
be restored by the addition of conducting salt. 

When the sheets have been sufficiently nickeled, they are 
allowed to drain off, then plunged into hot water, and after remov- 
ing the binding-screws, dried by gentle rubbing with fine sawdust 
free from sand and passed through a fine sieve to separate pieces 
of wood. In all manipulations, the unnickeled sides are placed 
together, while a piece of paper of the size and form of the sheets 
is laid, between the nickeled sides. 

The nickeled sheets are finally polished, which is effected by 
placing them upon supports and pressing against the revolving 
bob as previously described, the sheets being however only 
moderately moistened with oil, and not too much Vienna lime 
applied to the bob. Polishing is done first in one direction and 
then in another, at a right angle to this first. After polishing, 
the sheets are finally cleansed with a soft piece of cloth and 
impalpable Vienna lime, after which they should then show a pure 
white lustrous nickeling, free from cracks and stains, and bear 
several times bending and rebending without the nickeled deposit 
breaking or peeling off. 

Nickeling of tin plate. — For elegant and durable nickeling tin 
plate also requires previous coppering. The deposit is effected 
with a less powerful current than is used for sheet zinc. Scour- 
ing is done as described for sheet zinc, also the polishing of the 
nickeled tin plate. 

The treatment of copper and brass sheets differs from that of 
sheet zinc, in that rough sheets are first brushed with emery and 
then polished with the bob. After treating the sheets with hot 
caustic lye or lime paste, they are pickled by brushing them over 
with a solution of 1 part of potassium cyanide in 20 of water ; 
they are then thoroughly and quickly rinsed, and immediately 



168 ELECTRO-DEPOSITION OF METALS. 

brought into the bath. To avoid peeling off, the current must 
not be too strong. 

Nickeling of sheet iron and sheet steel. — Only the best quality 
of sheet should be used for this purpose. After rolling, the sheets 
are freed from scales by pickling, then passed through the fine 
rolls, and finally again pickled. If the nickeled sheets are not 
to exhibit a high degree of polish, it suffices to brush them before 
nickeling with a large broad fibre brush (p. Ill), and emery 
No. 00. But for a high lustre, such as is generally demanded, 
the sheets have first to be ground. For fine grinding the 
pickled sheets, broad massive cylinders of poplar wood are used, 
which are covered with leather and turned like the disks described 
on p. 107. These cylinders are 10 to 12 inches in diameter, and 
2 to 4 or more inches long, according to the size of the sheets. 
For the first grinding, the cylinders are coated with glue and 
rolled in emery No. 100 to 120, according to the condition of the 
sheets, while emery No. 00 is applied to the cylinders used for 
fine grinding. The grinding is succeeded by brushing, as described 
on p. 107. 

After preparing a sufficiently smooth surface, the sheets are at 
once rubbed with a rag moistened with petroleum, or, if preferred, 
with a rag and pulverized Vienna lime ; they are then scoured 
wet in the manner described for sheet zinc, p. 163. The scouring 
material must be liberally applied, especially if the sheets are to 
be directly nickeled without previous coppering, as is advisable. 
After rinsing off the lime paste, the sheets are brushed over with 
a brush dipped in very dilute sulphuric acid (1 part acid to 25 
water), rinsed off, then lightly brushed over once more with lime 
paste, again carefully rinsed, and immediately brought into the 
nickel bath. 

The current should be neither too strong nor too weak, but 
regulated so that the nickeling is of sufficient thickness in 15 to 
20 minutes without showing a tendency to peeling off. It is not 
advisable to try to obtain a heavy nickel deposit in a shorter 
time, because the deposit would lack in density, which is the 
principal requirement for nickeled sheet iron. 

After nickeling, the sheets are rinsed in clean water, then 
plunged into hot water and dried by rubbing with warm saw- 



DEPOSITION OF NICKEL AND COBALT. 169 

dust. After this operation, it is recommended to thoroughly dry 
the sheets in an oven heated to between 176° and 212° F., to 
expel any moisture from the pores, and then to polish them with 
Vienna lime and oil or with rouge. 

Nickeling of wire. — Nickeling of wire of iron, brass or copper 
is scarcely ever done on a large scale ; it is however believed that 
the nickeling of iron and steel wires— for instance, piano-strings — 
might be of advantage to prevent rust or at least to retard the 
commencement of oxidation as long as possible. 

To nickel single wires cut into determined lengths, according 
to the general rules already given, is simple enough ; but this 
method cannot be pursued with wire several hundred yards long 
rolled in coils as it occurs in commerce. Nickeling the wire in 
coils however cannot be done, as only the upper windings exposed 
to the anodes would acquire a coat of nickel. Hence it becomes 
necessary to unwind the coil, and for continuous working pass the 
wire at a slow rate through the cleansing and pickling baths as 
well as the nickel bath and hot reservoir, as shown in Fig. 77 in 
cross-section, and Fig. 78 in ground plan. 

The unwinding of the wire is effected by a slowly revolving 
shaft, upon which the nickeled wire again coils itself; but in the 
illustration the shaft is omitted. In Fig. 77 four wires run over 
the four rolls, a, mounted upon a common shaft, to the rolls b 
upon the bottom of the vat A, whereby they come in contact 
with a thickly fluid lime-paste in the vat, and are freed from 
grease. From the rolls b the wires run through the wooden 
cheeks i lined with felt, which retain the excess of lime-paste, 
and allow it to fall back into the vat. The wires then pass over 
the roll c to the roll d. Between these two rolls is the rose g, 
which throws a strong jet of water upon the wires, thereby free- 
ing them from adhering lime-paste. The roll d, as well as its 
axis, is of brass, and to the latter is connected the negative pole 
of the battery or dynamo, so that by carrying the wires over the 
roll d, negative electricity is conducted to them. From the roll d 
the wires run over the roll-bench s (Fig. 77) to the vat CJ which 
contains the nickel solution, so that they are subjected to the 
action of the anodes arranged in this vat on both sides of the 
wires. The wires then pass over the roll e, are rinsed under 



170 



ELECTRO-DEPOSITION OF METALS. 



the rose s, and run finally through a hot water reservoir and 
sawdust (these two apparatuses are not shown in the illustration) 




"* 

'.';i 



O* 



■o- 



o 



ri 



K/« 






-# «; 




to be again wound into coils. In case a high polish is required, 
the nickeled wires may be run under pressure through leather 
cheeks dusted with Vienna lime. 



DEPOSITION OF NICKEL AND COBALT. 171 

Nickeling wire-gauze. — Messrs. Louis Lang & Son obtained, in 
1881, a patent for a method of nickeling wire gauze, or wire to 
be woven into gauze, more especially for the purpose of paper 
manufacture. These wires, which are generally of copper or brass, 
are liable to be attacked by the small quantities of chlorine which 
generally remain in the paper pulp, by which the gauze wire 
eventually suffers injury. To nickel wire before it is woven, it is 
wound on a bobbin, and immersed in a nickel bath, in which it is 
coated with nickel in the usual way ; it is then unwound and re- 
wound on to another bobbin, and reimmersed in a nickel bath, as 
before, so as to coat such surfaces as were in contact with each 
other and with the first bobbin. To deposit nickel on the woven 
tissue it may either be coated in its entire length, as it leaves the 
loom, or in detached pieces. For this purpose the wire gauze is 
first immersed in a pickle bath, and next in the nickel solution. 
On leaving the latter it is rinsed and then placed in a hot air 
chamber, and when thoroughly dry may be rolled up again ready 
for use. 

Nickeling of knife-blades, sharp surgical instruments, etc. — Most 
electro-platers experience considerable trouble in nickeling sharp- 
edged instruments, the edges and points being invariably spoiled 
either by the deposit of nickel or in polishing. The following 
directions for the convenient nickeling of such instruments with- 
out any damage being done to the edges, are given by the Metal- 
arbeiter, and can be recommended: New articles which have 
not been used require no special preparation, they being at once 
freed from grease and brought into the bath. But instruments 
which have been used, and are partly or entirely coated with rust, 
must first be ground after the removal of the rust by chemical or 
mechanical means. The marks left by the stone or emery wheel 
are effaced by means of the circular brush. But in brushing, the 
edges are rendered dull if special precautionary measures are not 
used. For instance, the edge of a knife-blade must never come 
in contact with the brush. This is prevented by firmly pressing 
the blade flat upon a soft support of felt or cloth, so that the edge 
sinks somewhat into the support, without, however, cutting into 
it. The edge is then held downward and thus together with the 
support brought against the revolving brush. In this manner 



172 ELECTRO-DEPOSITION OF METALS. 

the blades may be vigorously brushed without fear of spoiling 
the edges. 

The treatment in giving them a high polish after nickeling is 
the same. Freeing from grease may be done in the usual manuer 
with lime-paste ; but must also be effected upon a soft support, 
the same as in polishing. After thorough rinsing in clean water 
the separate pieces, without being previously coppered, are brought 
directly into the nickel bath, the composition of which must, of 
course, be suitable for nickeling steel articles. The instruments 
are first coated with the use of a strong current, so that the depo- 
sition takes place slowly and with great uniformity. 

In suspending the articles in the bath, care should be had that 
neither a point nor an edge is turned towards the anodes. It is 
best to use a bath with anodes on one side only, and to suspend 
the blades with their backs towards the anodes. If, for any rea- 
son, the instruments are to be suspended between two rows of an- 
odes, the edges should be uppermost, as near as possible, to the 
level of the bath ; but they should never hang deep or downwards. 

After nickeling the instruments are polished for high lustre, but 
must always be exposed upon a soft support, as above described, 
to the action of a felt disk, or, still better, of a cloth bob. 

Nickeling of electrotypes, cliches, etc. — The advantages of nickel- 
ing electrotypes, etc, over steeling will be discussed under " Steel- 
ing/ 7 and hence only the most suitable composition of the nickel 
baths and the manipulations required will here be discussed. 

The nickel baths, according to formula III (page 139), and for- 
mula VII (page 141), are the most suitable for simple nickeling, 
because the ammonium sulphate not being present in too great an 
excess, as well as the presence of boric acid, has the effect of the 
nickel separating with great hardness. With nickeled electro- 
plates three times as large an edition can be printed as with 
plates of the same material not nickeled. 

It being a well-known fact that a fused alloy of nickel with 
cobalt possesses greater hardness than either of the metals by 
themselves, experiments proved that an electro-deposited nickel- 
cobalt alloy exhibited the same behavior, the greatest degree of 
hardness being attained with an addition of cobalt varying be- 
tween 25 and 30 per cent. For this deposit the term hard nickel- 



DEPOSITION OF NICKEL AND COBALT. 173 

ing is proposed, the most suitable baths for the purpose being 
prepared according to the following formulae : I. Nickel ammo- 
nium sulphate, 21.16 ounces; cobalt ammonium sulphate, 5.29 
ounces; ammonium sulphate, 8.8 ounces; water 15 quarts; or, 
II. Nickel ammonium sulphate, 21.16 ounces; cobalt ammonium 
sulphate, 5.29 ounces ; crystallized boric acid, 10.58 ounces ; 
water, 15 quarts. 

Bath No. I is prepared by simply dissolving the salts in heated 
water; and in case the bath is too acid, adding spirits of sal 
ammoniac until blue litmus paper is only slightly reddened. It 
is best to use rolled and cast anodes in equal proportions ; and 
when the bath becomes alkaline to restore its original slightly 
acid reaction by the addition of citric acid. 

To prepare bath No. II, dissolve the constituents by boiling; 
and in case not entirely neutral metallic salts have been used, add 
to the hot solution, with constant stirring, 1 to If ounces of nickel 
carbonate for the neutralization of free sulphuric acid which may 
be present. This bath must not be neutralized but worked with 
its strongly acid reaction, mixed anodes being also used. 

The bath prepared according to formula No. II. deserves the 
preference, it yielding a harder deposit than bath No. I. 

For the rest, the treatment of the baths is the same as that given 
for nickel baths of similar composition (pp. 139 and 141), and the 
process of hard nickeling does not essentially differ from ordinary 
nickeling. The suspending hooks are soldered to the backs of 
the plates by means of the soldering iron and a drop of tin ; or 
the plates are secured in holders of sheet-copper 0.11 inch thick, 
and f to 1 inch wide, of the form shown in Fig. 79. The print- 
ing surface is freed from grease by brushing with lime-paste, 
rinsed in water, and then brushed with a clean brush to remove 
the lime from the depressions. The plates are then hung in the 
bath and covered with a strong current. When everywhere coated 
with nickel the current is weakened and the deposit allowed grad- 
ually to augment. With an average duration of nickeling of 
15 to 20 minutes, with 2.8 to 3 volts, the deposit will, as a rule, 
be sufficiently resisting. 

The nickeled plates are rinsed in water, then plunged in hot 
water, and dried in sawdust, when the nickled printing surface may 



174 



ELECTRO-DEPOSITION OF METALS. 



be brushed over with a brush and fine whiting, it being claimed 
that plates thus treated take the printing ink better, while the first 
impressions of plates not brushed with whiting are somewhat dull. 



1 9. 




Mckel-facing is especially suitable for copper plates for color- 
printing, the nickel being not attacked like copper or iron, by 
vermillion. 

Recovery of nickel from old baths. — With the present low prices 
of nickel its recovery from old solutions scarcely pays. The use- 
lessness of the bath is in most cases due to two causes : the bath 
has either become too poor in metal, or it contains foreign metallic 
admixtures. In the first case the expense of evaporating with the 
further manipulation is out of proportion to the value of the nickel 
recovered, and in the second case the reduction of the foreign metals 
is inconvenient and connected with expenses making it unprofitable. 

Urquhart proposes the following plan for recovering nickel 
from old solutions : Make a saturated solution of ammonium 
sulphate in warm water and add to it the old nickel-plating solu- 
tion, with constant stirring, and, after the lapse of a few minutes, 
a granular precipitate of the double sulphate of nickel will begin 
to separate. The addition of ammonium sulphate should be from 



DEPOSITION OF NICKEL AND COBALT. 175 

time to time continued until the liquid is colorless. The precipi- 
tated salt is very pure and may be used directly in making a new 
bath. 

To improve defective nickeling. — With the basis-metal thoroughly 
cleansed defective places should not occur, but when they happen 
by accident or negligence recourse is had to "doctoring." The 
" doctor" is arranged as follows : A piece of stout copper wire is 
bent in the form of a hook at each end ; a fragment of nickel 
anode is then fastened firmly to one of the hooks with a piece of 
twine. The fragment of anode is then wrapped in several folds 
of muslin, the second hook connected by a wire to the anode-rod 
of the bath, and the article put in contact with the negative elec- 
trode. The rag end is now dipped in the nickel bath, applied to 
the defective spot, and allowed to rest upon it for a few moments, 
then dipped again and reapplied. By repeatedly dipping the rag 
in the nickel bath and applying it in this way a sufficient coating 
of nickel may be given in a few minutes so that if the operation 
is skilfully performed, no trace of the patch will be observable 
after polishing. 

Nickeling by contact and boiling. — Franz Stolba has described 
a nickeling process by contact, which is executed as follows : — 

In a bright copper kettle heat to boiling a concentrated solution 
of zinc chloride with an equal or double the volume of soft water, 
and then add drop by drop pure hydrochloric acid until the pre- 
cipitate formed by diluting the zinc chloride solution with water 
disappears. Then add as much zinc powder as will lie upon the 
point of a knife, the effect of this addition being that the copper 
of the kettle as far as it comes in contact with the solution is in 
a few minutes zincked. Now bring into the kettle sufficient 
nickel salt, best nickel sulphate, to color the fluid perceptibly 
green, then introduce the articles to be nickeled together with 
small pieces of sheet zinc or zinc wire, so as to present many 
points of contact, and continue boiling. With a correct execution 
of the process it is claimed the articles will be uniformly nickeled 
in 15 minutes; if such is not the case the boiling must be con- 
tinued, fresh pieces of zinc added, or if the solution does not 
appear sufficiently green, fresh nickel salt introduced. 

For the success of the process several conditions are necessary. 



176 ELECTRO-DEPOSITION OF METALS. 

The metallic articles must be thoroughly free from grease, as 
otherwise no deposit of nickel is formed on the greasy places. 
In boiling, the solution must not become turbid by the separation 
of basic zinc salt, nor acid by free hydrochloric acid, otherwise 
the nickeling will be dull and blackish. Hence, any turbidity 
must be at once removed by adding drop by drop hydrochloric 
acid, and too great acidity by the careful addition of solution of 
carbonate of soda. The articles thus nickeled are to be thoroughly 
washed with water, dried, and polished with whiting. 

Since by this process stains are readily formed, especially when 
nickeling polished iron and steel articles, on the places where the 
metal to be nickeled comes in contact with the zinc, Stolba in later 
experiments omitted the zinc, and thus the contact process becomes 
a boiling process. To a 10 per cent, solution of zinc chloride add 
enough nickel sulphate to give the solution a deep green color and 
then heat, best in a porcelain vessel, to the boiling point. Then 
without troubling about the turbidity of the bath caused by the 
separation of a basic zinc salt, immerse the objects previously 
cleansed and freed from grease, in it in such a way that they do 
not touch each other, or at least only in a few places, and keep 
the whole boiling 30 to 60 minutes, from time to time replacing 
the water lost by evaporation. The after-treatment is the same 
as given above for the contact process ; the deposit of nickel is of 
course very thin. 

This process, while suitable for the amateur, cannot be recom- 
mended to the professional electro-plater, the results not being 
sufficiently sure. A thin deposit of nickel of a light color may 
be obtained upon brass articles, but that upon iron articles is dark 
and mostly stained. 

Small articles, which are not to be nickeled by the battery, are 
preferably coated by contact with cobalt by the process to be de- 
scribed later on, under " Electro-cobalting." The higher price of 
cobalt salts makes little difference, small quantities only being 
required, and the color of cobalt can scarcely be distinguished 
from that of nickel. 

By boiling a solution of 8J ozs. of nickel ammonium sulphate 
and 8J ozs. of ammonium chloride in 1 quart of water, together 
with clean iron filings free from grease, and introducing into the 



DEPOSITION OF NICKEL AND COBALT. 177 

fluid copper or brass articles, the latter become coated with a thin 
layer of nickel capable of bearing light polishing. The nickel 
solution has to be frequently renewed. 

According to R. Kaiser, an alloy containing nickel may be de- 
posited upon articles by proceeding as follows : Melt 1 part of 
copper and 5 of tin, and granulate the fused mass by pouring it 
through a heated sheet iron sieve into a bucket filled with water. 
Boil the granulated metal thus obtained with tartar, free from 
lime, and add for every 100 parts by weight of granulated metal 
0.5 part of glowed nickel oxide. Then bring the brass or copper 
articles previously freed from grease and pickled, into the boiling 
fluid, and after boiling for a short time they will appear coated 
with a white alloy resembling German silver. The addition of 
nickel oxide must from time to time be repeated. Iron and steel 
articles are to be previously coppered. By adding nickel car- 
bonate to this bath, it is claimed, coats richer in nickel and of a 
darker color than that of platinum to blue-black are obtained. 

Deposits of nickel alloys. — From suitable solutions of the 
metallic salts nickel may be deposited together with copper and 
tin, as well as with copper and zinc. With the first combination, 
especially all tones from copper- red to gold shade may be obtained 
according to which metal predominates, or, according to the cur- 
rent-strength which is conducted into the bath, as is also the case 
in brassing. 

A suitable bath for coating metallic articles with an alloy of 
nickel, copper, and tin, for which the term nickel bronze is pro- 
posed, is obtained by dissolving the metallic phosphates in sodium 
pyrophosphate. By mixing solution of blue vitriol with solution 
of sodium phosphate, cupric phosphate is precipitated which is 
filtered off and washed. In the same manner nickel phosphate 
is prepared from a solution of nickel sulphate. These phosphates 
are then, each by itself, dissolved in a concentrated solution of 
sodium pyrophosphate, while chloride of tin is directly dissolved 
in sodium pyrophosphate until the turbidity, at first rapidly dis- 
appearing, disappears but slowly. 

Nothing definite can be said in regard to the mixing propor- 
tions of these three solutions, because the proportions will have 
to be varied according to the desired color of the deposit; the 
12 



178 ELECTRO-DEPOSITION OF METALS. 

operator, however, will soon find out of which solution more 
must be added in order to obtain the tone desired. 

For depositing an alloy of nickel, copper, and zinc, solutions 
of cupric sulphate (blue vitriol) and zinc white in potassium 
cyanide, to which is added an ammoniacal solution of nickel car- 
bonate, may be advantageously used. 

According to a French process, a deposit of German silver 
may be obtained as follows : Dissolve a good quality of German 
silver in nitric acid and add with constant stirring solution of potas- 
sium cyanide until all the metal is precipitated as cyanide. The 
precipitate is then filtered off, washed, dissolved .in potassium 
cyanide, and the solution diluted with double the volume of 
water. This process, however, does not seem very feasible, since 
nickel separates with difficulty from its cyanide combination. 

Watt recommends the following method : Cut up into small 
pieces sheet German silver about 1 oz., place the strips in a 
glass flask, and add nitric acid diluted with an equal bulk of 
water. Assist the solution of the metal by gentle heat. When 
the red fumes cease to appear in the bulb of the flask, decant the 
liquor, and apply fresh acid, diluted as before, to the undissolved 
metal, taking care to avoid excess ; it is best to leave a small quan- 
tity of undissolved metal in the flask, by which an excess of acid 
is readily avoided. The several portions of the metallic solutions 
are to be mixed and diluted with about 3 pints of cold water in a 
gallon vessel. Next dissolve about 4 ozs. of carbonate of potash 
in a pint of water, and add this gradually to the former, with 
gentle stirring, until no further precipitation takes place. The 
precipitate must be several times washed with hot water, and 
then redissolved by adding a strong solution of cyanide, with 
stirring, and about 1 oz. of liquid ammonia. To avoid adding 
too great an excess of cyanide, it is a good plan, when the pre- 
cipitate is nearly all dissolved, to let it rest for half an hour or 
so, then decant the clear liquor, and dissolve the remainder of the 
precipitate separately. A small excess of cyanide solution may 
be added as " free cyanide," and the whole mixed together and 
made up to one gallon with cold water. The solution should 
then be filtered or allowed to repose for about 1 2 hours, and the 
clear liquor then carefully decanted from any sediment which may 



DEPOSITION OF NICKEL AND COBALT. 179 

be present from cyanide impurities. The bath must be worked 
with a German-silver anode, which should be of the same quality 
as that from which the solution is prepared ; a Bunsen battery 
should be employed as the source of electricity, or a dynamo- 
machine. 

2. Cobalting. 

Properties of cobalt. — Cobalt has nearly the same color as nickel, 
with a slightly reddish tinge; its specific gravity is 8.56. It is 
exceedingly hard, highly malleable and ductile, and capable of 
taking a polish. It is slightly magnetic, and preserves this 
property even when alloyed with mercury. It is rapidly dis- 
solved by nitric acid and slowly by dilute sulphuric and hydro- 
chloric acids. 

For cobalting, the baths given under nickeling may be used 
by substituting for the nickel salt a corresponding quantity of 
cobalt salt. By observing the rules given for nickeling, the 
operation proceeds with ease. Anodes of metallic cobalt are to 
be used in place of nickel anodes. 

Nickel being cheaper and its color somewhat whiter, electro- 
plating with cobalt is but little practised. On account of the 
greater solubility of cobalt it is, however, under all circumstances, 
to be preferred for facing valuable copper plates for printing. 

According to the more or less careful adjustment of such plates 
in the press, many places of the facing are more or less attacked, 
and it may be desired to remove the coating and make a fresh 
deposit. For this purpose, Gaiife has proposed the use of cobalt 
in place of nickel, because the former dissolves slowly but com- 
pletely in dilute sulphuric acid. He recommends a solution of 
1 part of chloride of cobalt in 10 of water. The solution is to be 
neutralized with aqua ammonia, and the plates are to be electro- 
plated with the use of a moderate current. 

Cobalt precipitated from its chloride solution does not however 
yield a hard coating, and hence the following bath is recommended 
for the purpose : Double sulphate of cobalt and ammonium 21 
ozs., cobaltous carbonate 0.8 oz., crystallized boric acid 10J ozs., 
water 10 quarts. 



180 ELECTRO-DEPOSITION OF METALS. 

The bath is prepared in the same manner as No. VII, given 
under " Nickeling." It requires a tension of 2.5 to 2.75 volts. 

To determine whether and how much copper is dissolved in 
stripping the cobalt deposit from cobalted copper plates, a copper 
plate with a surface of 7f square inches was coated with 7.71 
grains of cobalt and placed in dilute sulphuric acid (1 part acid 
of 66° Be. to 12.5 parts of water). After the acid had acted 
for 16 hours, the cobalt deposit was partially dissolved and had 
partially collected in lamina upon the bottom of the vessel, the 
copper plate being entirely freed. On weighing the copper-plate 
it was shown that it had lost about 0.0063 per cent., this loss 
being apparently chiefly from the back of the plate, the engraved 
side exhibiting no trace of corrosion. This experiment proved 
that there is no danger of destroying the copper-plate by strip- 
ping the cobalt deposit with dilute sulphuric acid, provided the 
operation is executed with due care and attention. 

Warren has recently described a cobalt solution which can be 
decomposed in a single cell apparatus, and for this reason would 
seem suitable for electro-plating small articles en masse. For 
the preparation of this bath dissolve 3J ounces of chloride of co- 
balt in as little water as possible, and compound the solution with 
concentrated solution of Rochelle salt until the voluminous pre- 
cipitate at first formed is almost entirely re-dissolved, and then 
filter. Bring the bath into a vessel and place the latter in a clay- 
cell filled with concentrated solution of sal ammoniac or of com- 
mon salt and containing a zinc cylinder. Connect the objects to 
be plated to the zinc by a copper wire and allow them to dip in 
the cobalt solution. With a closed current the objects become 
gradually coated with a lustrous cobalt deposit which, after 2 
hours, is sufficiently heavy to bear vigorous polishing with the 
bob. Zinc may be coated in the same manner. 

The following solution has been recommended by Mr. G. W. 
Beardslee, of Brooklyn, N.Y., and is claimed to yield a good deposit 
of cobalt which is very white, exceedingly hard, and tenaciously 
adherent : Dissolve pure cobalt in boiling hydrochloric acid and 
evaporate the solution to dryness. Next dissolve 4 to 6 ozs. of 
the resulting salt in 1 gallon of distilled water, to which add 
liquid ammonia until it turns red litmus paper blue. The solu- 



DEPOSITION OF COPPER, BRASS, AND BRONZE. 181 

tioo being thus rendered slightly alkaline is ready for use. A 
battery power of from two to five Sinee cells will be sufficient to 
do good work. Care must be had not to allow the solution to lose 
its slightly alkaline condition upon which the whiteness, uni- 
formity of deposit, and its adhesion to the basis-metal greatly 
depend. 

Cobalting by contact. — While nickeling by contact with zinc 
yields only incomplete results, the cobalting of copper and brass 
articles succeeds very well with the use of the following bath : 
Crystallized cobalt sulphate 0.35 oz., crystallized sal ammoniac 
0.07 oz., water 1 quart. Heat the bath to between 104° and 
122° F., and immerse the previously cleansed and pickled articles 
in the bath, bringing them in contact with a bright zinc surface 
not too small ; for small articles a zinc sieve may be used. In 
3 or 4 minutes the coating is heavy enough to bear vigorous 
polishing. 



CHAPTER VIII. 



1. Coppering. 

Properties of copper. — Copper has a characteristic red color, and 
possesses strong lustre ; it is very tenacious, may be rolled to thin 
lamina, and readily drawn to fine wire. The specific gravity of 
wrought copper is 8.95, and of cast 8.92. Copper fuses more 
readily than gold, but with greater difficulty than silver. 

In a humid atmosphere containing carbonic acid, copper becomes 
gradually coated with a green deposit of basic carbonate ; when 
slightly heated, it acquires a red coating of cuprous oxide, and 
when strongly heated, a black coating of cupric oxide with some 
cuprous oxide. Copper is most readily attacked by nitric acid, 
but is slowly dissolved when immersed in heated hydrochloric or 
sulphuric acid ; with exclusion of the air, it is not dissolved by 
dilute sulphuric or hydrochloric acid, and but slightly with 
admission of the air. Liquid ammonia causes a rapid oxidation 



182 ELECTRO-DEPOSITION OF METALS. 

of copper in the air and the formation of a blue solution. An 
excess of potassium cyanide dissolves copper. Sulphuretted 
hydrogen blackens bright copper. 

Copper baths. — The composition of these baths depends on the 
purpose for which they are to serve, and in the following the most 
approved baths are mentioned, with the exception of the acid 
copper bath used for plastic deposits of copper, which will be 
discussed later on under " Copper galvanoplasty." 

In most cases the more electro-positive metals, zinc, iron, tin, 
etc., are to be coppered either as preparation for the succeeding 
process of nickeling, silvering or gilding, or to protect them against 
oxidation or for the purpose of decoration. The above-mentioned 
electro-positive metals, however, decompose acid copper solutions 
and separate from them pulverulent copper, while an equivalent 
portion of zinc, iron, tin, etc., is dissolved. For this reason, such 
solutions of copper cannot be used for coating these metals for 
this purpose, alkaline copper baths being exclusively employed, 
which may be arranged into two groups — into those containing 
potassium cyanide, and into those without it. 

Hassauer prepares a copper bath by dissolving 3 J ozs. of copper 
cyanide in a solution of 17 J ozs. of 70 per cent, potassium cyanide 
in 3 quarts of water, boiling, filtering, and diluting with 7 quarts 
Of water to a 10 quart bath. This bath works very well when 
heated to between 113° and 122° F., but when used cold requires 
a very strong current, and hence the use of the following formulae 
is recommended : — 

Copper baths for iron and steel articles. — I. To be used at the 
ordinary temperature. Water 10 quarts, crystallized bisulphite of 
soda 7 ozs., carbonate of soda 14 ozs., neutral acetate of copper 
7 ozs., 75 per cent, potassium cyanide 7 ozs., spirits of sal ammo- 
niac 4.4 ozs. 

II. To be used at between 140° and 158° F. — Water 10 quarts, 
crystallized bisulphite of soda 2f ozs., crystallized carbonate of 
soda 7 ozs., neutral acetate of copper 7 ozs., 75 per cent, cyanide 
of potassium 9 j ozs., spirit of sal ammoniac 4 ozs. 

The baths are best prepared as follows : Dissolve the bisulphite 
and carbonate of soda in one-half the water, the potassium cyanide 
in the other half, and mix the copper salt with the spirit of sal 



DEPOSITION OF COPPER, BRASS, AND BRONZE. 183 

ammoniac ; then pour the blue ammoniacal copper solution into 
the solution of the soda salts, and finally add the potassium 
cyanide solution ; the bath will then be clear and colorless. Boil- 
ing, though not absolutely necessary, is of advantage, after which 
the solution is to be filtered. 

The above formula? are given by Roseleur. However, accord- 
ing to investigations made, the excess of carbonate of soda in 
formula I. serves no special purpose, but on the contrary, in 
many cases, is directly detrimental ; neither is the use of ammonia 
of any special advantage, and it may just as well, or rather better, 
be omitted. Further, the use of separate baths for cold and warm 
coppering is at least questionable. It is believed that a single 
bath suffices for both cases, heating having been found of special 
advantage only for rapid and thick coppering or for obtaining 
particular shades which are produced with difficulty in the cold 
bath, but without trouble in the heated bath. 

The following formula? may be highly recommended, a copper 
bath composed according to it always yielding good and sure 
results : — 

III. Water 10 quarts, crystallized carbonate of soda 8J ozs., 
crystallized bisulphite of soda 7 ozs., neutral acetate of copper 
7 ozs., 98 or 99 per cent, potassium cyanide 8J ozs. 

The bath is prepared as follows : Dissolve in 7 quarts of warm 
water the carbonate of soda, gradually add the bisulphite of soda 
to prevent violent effervescence, and then add, with vigorous 
stirring, the acetate of copper in small portions. Dissolve the 
potassium cyanide in 3 quarts of cold water, and mix both solu- 
tions when the first is cold. By thorough stirring with a clean 
Avooden stick, a clear solution is obtained, which is best boiled for 
half an hour and then filtered. This bath does not require a 
strong current, and yields an especially heavy coppering of a 
beautiful red color ; a current of 0.4 ampere at a tension of 3 to 
3.5 volts is calculated for 15J square inches of surface of objects. 

Annealed sheets of pure copper with as large a surface as pos- 
sible serve as anodes. In all baths containing cyanide the anodes 
become, in a comparatively short time, coated with a greenish 
slime consisting of a basic copper cyanide mostly soluble in excess 
of potassium cyanide. When a very thick formation of such slime 



184 ELECTRO-DEPOSITION OF METALS. 

takes place, potassium cyanide is wanting, and has to be added. 
Other phenomena appearing in copper baths containing cyanide 
may as well here be mentioned. Too large an excess of potassium 
cyanide causes a strong evolution of hydrogen bubbles on the 
objects ; but no deposition of copper, or only a slight one, takes 
place, which besides has the tendency to peel off. If this pheno- 
menon appears after adding potassium cyanide, the excess can be 
readily removed by the addition of a copper salt, best cyanide of 
copper, stirred with a small quantity of the bath to a thinly-fluid 
paste. After each addition, a test is made whether an object 
suspended in the bath is rapidly and regularly coppered ; if such 
is not the case, the addition of cyanide of copper is repeated until 
the bath works in a faultless and correct manner. On the other 
hand, a deposit may not be formed for the want of potassium 
cyanide, which is already indicated by a thick formation of slime 
on the anodes, and by the fluid acquiring a pale blue color ; or 
the metallic content of the bath may be too small. In the first 
case, a slight addition of potassium cyanide will cause the bath 
to work correctly, but to augment the metallic content of the 
bath, an addition of solution of copper cyanide in potassium 
cyanide is required, it being always best to introduce together 
with the metallic cyanide solution a small quantity of carbonate 
and bisulphite of soda, in order to decrease the resistance to con- 
ductivity. In every bath containing cyanide, each addition, and 
especially that of a metallic salt, causes a momentary irritation, 
and it will be found that a bath augmented by additions works 
irregularly for some hours. To overcome this, it is recommended 
to boil the bath or work it through with the current as already 
mentioned on p. 131. 

For coppering zinc articles, Roseleur recommends the follow- 
ing bath : — 

IV. Water 10 quarts, tartar, free from lime, 6.7 ozs., crystal- 
lized carbonate of soda 15 ozs., blue vitriol 6.7 ozs., caustic soda 
lye of 16° Be. f lb. 

To prepare this bath, dissolve the tartar and the crystallized 
carbonate of soda in § of the water, and the blue vitriol in the 
remaining J, and mix both solutions. Filter off the precipitate, 



DEPOSITION OF COPPER, BRASS, AND BRONZE. 185 

dissolve it in the caustic soda lye, and add this solution to the 
other. 

This hath works very well, and may be recommended to electro- 
platers who copper zinc exclusively, but where all kinds of metals 
are to be coppered, bath No. Ill is to be preferred, it yielding 
equally good results for zinc. 

For small zinc objects which are to be coppered in a sieve, bath 
No. Ill is used, it being heated for this purpose, and a little more 
potassium cyanide added. Roseleur recommends for the same 
purpose a bath composed as follows : — 

Y. Water 10 quarts, crystallized bisulphite of soda If ozs., 
neutral acetate of copper 8 ozs., 75 per cent, potassium cyanide 
12 J ozs., and ammonia } oz. The bath is prepared in the same 
manner as formulas I. to III. 

In preparing copper baths, the acetate of copper prescribed in 
the preceding formula may be replaced by the carbonate or sul- 
phate, the substitution of the latter, after its previous conversion 
into carbonate, being of special advantage in order not to impart 
to the bath too great a resistance by the potassium sulphate, formed 
by reciprocal decomposition. The following formula is especially 
suitable for the use of sulphate of copper (blue vitriol) : — 

VI. Blue vitriol 

Crystallized carbonate of soda . 



10 J ozs. 


10} " 


10 quarts, 


7 ozs. 


°2 


°2 



Water 

Crystallized bisulphite of soda . 
Crystallized carbonate of soda . 
98 to 99 per cent, potassium cyanide . 

First dissolve the 10} ozs. of blue vitriol and the 10} ozs. of 
crystallized carbonate of soda, each by itself, in hot water, and 
mix the two solutions ; allow the precipitate of carbonate of copper 
to settle, and pour oif the supernatant clear fluid. Then pour 
upon the precipitate 5 quarts of water, add the bisulphite of soda, 
next the carbonate of soda, and mix this solution with the solu- 
tion of the potassium cyanide in 5 quarts of water. The fluid 
rapidly becomes clear and colorless, when it is boiled and filtered. 

Of the many directions for copper baths without potassium 



186 ELECTRO-DEPOSITION OF METALS. 

cyanide , to which also belongs the bath prepared according to 
formula IV., and which have chiefly been proposed for coppering 
cast and wrought iron, only a few need be mentioned as being 
actually available. 

Weil obtains a deposit of copper in a bath consisting of a solu- 
tion of blue vitriol in an alkaline solution of tartrate of potas- 
sium or sodium. Such a bath is composed as follows : — 

VII. Water 10 quarts, potassium sodium tartrate (Rochelle 
salt) 53 ozs., blue vitriol 10 J ozs., 60 per cent, caustic soda 28 ozs. 

The chief purpose of the large content of caustic soda is to 
keep the tartrate of copper, which is almost insoluble in water, 
in solution. According to Weil, the coppering may be executed 
in three different ways, as follows : — 

The iron articles tied to zinc wires or in contact with zinc strips 
are brought into the bath ; the coppering thus taking place by con- 
tact. Or porous clay cells are placed in the bath containing the 
articles ; these clay cells are filled with soda lye, in which zinc 
plates connected with the object-rods are allowed to dip, the 
arrangement in this case forming an element with which, by the 
solution of the zinc in the soda lye, a current is produced, which 
effects the decomposition of the copper solution and the deposi- 
tion. When saturated with zinc, the soda lye becomes ineffec- 
tive, and according to Wiel, it may be regenerated by the addition 
of sodium sulphide, which separates the dissolved zinc as zinc sul- 
phide. The third method of coppering consists in the use of the 
current of a battery or of a. dynamo-machine, in which case copper 
anodes have, of course, to be employed. 

A copper bath recommended by Walenn is composed of a solu- 
tion of equal parts of tartrate of ammonia and potassium cyanide 
in which 3 to 5 per cent, of copper (in the form of blue vitriol 
or moist cupric hydrate) is dissolved. The bath is to be heated 
to about 140° F. 

Gauduin's copper bath consists of a solution of oxalate of copper 
with oxalate of ammonia and free oxalic acid. Fontaine asserts 
that the bath works well, when heated to between 140° and 
150° F. 

Copper baths containing cyanide cannot be brought into pitched 
vats, vats of stone-ware or enamelled iron being used for smaller 



DEPOSITION OF COPPER, BRASS, AND BRONZE. 187 

baths, and for larger, basins of brick set in cement, or iron reser- 
voirs lined with ebonite. 

Execution of coppering. — The general rules given under nickel- 
ing, as regards the suitable composition of the bath, correct selec- 
tion of anodes, careful scouring and pickling of the objects and 
proper current-strength also apply to coppering. 

As previously mentioned, annealed sheets of pure copper are 
used as anodes, the surface of which should be at least twice as 
large as that -of the objects to be coppered. Even with a correct 
content of potassium cyanide in the bath the anodes readily tarnish 
and must from time to time be brightened by scouring with saud 
or by pickling ; if the latter method be adopted, care should be 
had not to inhale the escaping vapors which contain prussic acid. 

The preliminary scouring and pickling of the articles to be 
coppered are executed according to the directions given on page 1 25. 
The same precautions discussed under nickeling have to be used 
in suspending the objects in the bath, and the directions given 
there for the suitable arrangement of the anodes, etc., also apply 
to coppering ; however, a copper bath conducting better than a 
nickel bath, the distance between the anodes and the objects may, 
if necessary, be somewhat greater. 

With a proper arrangement of the anodes and correct regula- 
tion of the current, the objects should be entirely coated with 
copper in a few minutes after being hung in the bath. In five 
to ten minutes the objects are taken from the bath and brushed 
with a scratch-brush of not too hard brass wires, whereby the 
deposit should everywhere show itself to be durable and adherent. 
Defective places are especially thoroughly scratch-brushed, scoured 
and pickled ; the objects are then returned to the bath. For solid 
and heavy coppering the objects remain in the bath until the 
original lustre and red tone of the coppering disappear and pass 
into a dull discolored brown ; at this stage the objects are again 
scratch-brushed until they show lustre and the red copper color, 
whereby it is of advantage to moisten them with tartar water. They 
are then again returned to the bath, where they remain until the 
dull discolored tone reappears. They are then taken out, scratch- 
brushed bright, rinsed in several clean waters, plunged into hot 
water, and finally dried, first in sawdust and then thoroughly, 



188 ELECTRO-DEPOSITION OF METALS. 

at a high temperature, in the drying chamber. Special attention 
must be paid to the thorough washing of the coppered objects, 
because, if anything of the bath containing cyanide remains in the 
depressions or pores, small, dark, round stains appear on those 
places which cannot be removed, or at least only with great diffi- 
culty, they reappearing again in a short time after having been 
apparently removed. This formation <5f stains appears especially 
frequently upon coppered (as well as brassed) iron and zinc cast- 
ings, which cannot be produced without pores. To prevent the 
formation of these stains the following method is recommended : 
Since the rinsing in many waters, and even allowing the objects to 
lie for hours in running water, offers no guarantee that every trace 
of fluid containing cyanide has been removed, the objects are 
brought into a slightly acid bath which decomposes the fluid, a 
mixture of 1 part of acetic acid and 50 parts of water being well 
adapted for the purpose. The objects are allowed to remain in 
this mixture for three to five minutes, when they are rinsed off 
in w T ater and dipped for a few minutes in dilute milk of lime. 
They are finally rinsed off and dried. Coppered castings thus 
treated will show no stains. 

O. Schulz obtained a patent for the following method for re- 
moving the hydrochloric acid from the pores, and thus preventing 
the formation of stains : The plated objects are placed in a room 
which can be hermetically closed. The air is then removed from 
the room by the introduction of steam of a high tension, and by 
means of an air-pump, and water sprinkled upon the objects. 
By this treatment in vacuum the fluid in the pores comes to the 
surface and the salt solution is removed by the water sprinkled 
over the articles. 

After drying, the deposit of copper, if it is to show high lustre, 
is polished with soft disks of fine flannel and dry Vienna lime ; 
commercial polishing red FFF, moistened with a little alcohol, is 
also an excellent polishing agent for copper and all other soft 
metals. 

As is well known massive copper rapidly oxidizes in a humid 
atmosphere, and this is the case to a still greater extent with elec- 
tro-deposited copper. Hence, the coppered objects, if they are 
not to be further coated with a non-oxidizing metal, have to be 



189 

provided with a colorless, transparent coat of lacquer (see " Lac- 
quering"). 

It frequently happens that slightly coppered (as well as slightly 
brassed) objects, especially of zinc, after some time, become entirely 
white and show no trace of the deposit. This is due to the de- 
posit penetrating into the basis metal, as already explained on p. 
133. Lacquering in this case is of no avail, the deposit also 
disappearing under the coat of lacquer. The only remedy 
against this phenomenon is a heavier deposit. 

If the coppered objects are to be coated with another metal, 
drying is omitted, and after careful rinsing they are directly 
brought into the respective bath, or into the quicking pickle if 
as, for instance, in silvering, quicking has to be done. In such 
cases where the copper deposit only serves as an intermediary for 
the reception of another metallic coating, the objects need not to 
be coppered as thickly, as previously described, by treating them 
three times in the bath. Preliminary coppering for 5 to 10 
minutes suffices in all cases which is succeeded by scratch-brush- 
ing in order to be convinced that the deposit adheres firmly and 
that the basis metal is uniformly coated. The objects are then 
hung in the bath for 5 to 10 minutes longer with a weak current. 
In coppering sheet iron or sheet zinc which is to be nickeled, 
the sheets are taken from the bath after 3 to 5 minutes, at any 
rate while they still retain their lustre, scratch-brushing being 
in this case omitted. For coppering such sheets a current- 
density of 0.5 ampere with a tension of 3.5 to 4 volts is required. 
The treatment of copper baths when they become inactive or 
exhibit other abnormal phenomena has been referred to on p. 
184 ; all other rules for galvanic baths given in Chap. VI., must 
here also be observed. 

For coppering small articles en masse in sieves it is recommended 
to have the copper baths right hot ; for the rest, the process is 
the same as that given for nickeling small articles en masse on 
p. 153. 

Coppering by contact and dipping. — According to LudersdorfF, 
a solution of tartrate of copper in neutral potassium tartrate 
serves for this purpose. A suitable modification of this bath is 
as follows: Heat 10 quarts of water to 140° F., add 2 lbs. of 



190 ELECTRO-DEPOSITION OF METALS. 

pulverized tartar (cream of tartar) free from lime, and 10 J ozs. of 
carbonate of copper. Keep the fluid at the temperature above 
mentioned until the evolution of gas due to the decomposition of 
the carbonate of copper ceases, and then add in small portions, 
and with constant stirring, pure whiting until effervescence is no 
longer perceptible. Filter off the fluid from the tartrate of lime 
separated and wash the precipitate so that the filtrate inclusive of 
the wash water amounts to 10 to 1 2 quarts. 

Zinc is coppered in this bath by simple immersion ; other 
metals have to be brought in contact with zinc. 

Another contact coppering bath is that prepared according to 
formula VII. (p. 186), proposed by Weil. In this bath zinc is 
also coppered by simple immersion, and copper and iron in con- 
tact with zinc strips. 

According to Bacco, a copper bath in which zinc may be cop- 
pered by immersion, and iron and other metals in contact with 
zinc, is prepared by adding to a saturated solution of blue vitriol, 
potassium cyanide solution until the precipitate of cyanide of 
copper which is formed is again dissolved. Then add ^ to J of 
the volume of liquid ammonia and dilute with water to 8° Be. 

The so-called brush-coppering which has been recently recom- 
mended may here be mentioned. This process may be of practi- 
cal advantage for coppering very large objects which by another 
method could only be coated with difficulty. The deposit of 
copper is, of course, very thin. The process is executed as 
follows : The utensils required are two vessels of sufficient size 
each provided with a brush, preferably so wide that the entire 
surface of the object to be treated can be coated with one appli- 
cation. One of the vessels contains a strongly saturated solution 
of caustic soda and the other a strongly saturated solution of 
blue vitriol. For coppering, the well cleansed object is first uni- 
formly coated with a brushful of the caustic soda solution, and 
then also with a brushful of the blue vitriol solution. A quite 
thick film of copper is immediately deposited upon the object. 
Care must be had not to take the brush too full and not to touch 
the places once gone over, the second time, as otherwise the layer 
of copper does not adhere firmly. 

Many iron and steel objects are provided with a thin film 



DEPOSITION OF COPPER, BRASS, AND BRONZE. 191 

of copper in order to give them a more pleasing appearance. 
For this purpose a copper solution of 10 quarts of water, If ozs. 
of blue vitriol and If ozs. of pure concentrated sulphuric acid 
may be used. Dip the iron or steel objects previously freed from 
grease and oxide for a moment in the solution, moving them con- 
stantly to and fro, then rinse them immediately in ample water 
and dry. By keeping the articles too long in the solution the 
copper separates in a pulverulent form and does not adhere. 

Steel pens, needles, eyes, etc., may be coppered by diluting the 
copper solution just mentioned with double the quantity of water, 
moistening sawdust with the solution and revolving the latter 
together with the articles to be coppered in a wooden tumbling 
box (p. 106). 

The inlaying of depressions of coppered art-castings with 
black may be done in different ways. Some blacken the ground 
by applying a mixture of spirit lacquer with soot and graphite, 
while others use oil of turpentine with soot and a few drops of 
copal lacquer. A very thin nigrosin lacquer mixed with finely 
pulverized graphite is very suitable for the purpose. When the 
lacquer is dry the elevated places which are to show the copper 
color are cleansed with a linen rag moistened with alcohol. 

Electrolytically coppered articles may be inlaid black by coat- 
ing them, after thorough scouring and pickling, with arsenic in 
one of the baths given under " Electro-deposition of Arsenic/ 7 
and after drying in hot water and sawdust, freeing the surfaces 
and profiles, which are to appear coppered, from the coating of 
arsenic by polishing upon a felt disk. If this polishing is to be 
avoided the portions which are not to be black may be coated 
with covering lacquer, and arsenic deposited upon the places re- 
maining free. 

For coloring, "platinizing and oxidizing of copper see the proper 
chapter. 

2. Brassing (Cuivre-poli Deposit). 

Brass is an alloy of copper and zinc whose color depends on 
the quantitative proportions of both metals. The alloys known 
as yellow brass, red bi*ass (similor, tombac) consists essentially of 



192 ELECTRO-DEPOSITION OF METALS. 

copper and zinc, while those known as bell-metal, gun-metal and 
the bronzes of the ancients are composed of copper and tin. 
Modern bronzes contain copper, zinc, and tin. 

The behavior of brass towards acids is nearly the same as that 
of copper ; it oxidizes, however, less readily in the air, is harder 
than copper, malleable, and can be rolled and drawn into wire. 

Brass baths. — According to the plan pursued in this work, only 
the most approved formulae will be given. There exist a large 
number of directions for brass baths ; but we share the opinion of 
Roseleur, that a brass bath containing copper and zinc salts in 
nearly equal proportions is the most suitable and least subject to 
disturbances. A brass bath is to be considered as a mixture of 
solutions of cyanide of copper and cyanide of zinc, or of other 
copper-zine salts in the most suitable solvent ; and since a solu- 
tion of cyanide of copper requires a different current-strength 
from one of zinc salt, it will be seen that according to the greater 
or smaller current-strength, now more of the one, and now more 
of the other metal is deposited, which, of course, influences the 
color of the deposit. Hence the proper regulation of the current 
is the chief condition for obtaining beautiful deposits, let the 
bath be composed as it may. 

For all baths containing more than one metal in solution, it 
may be laid down as a rule that the less positive metal is first 
deposited. In a brass bath copper is the negative and zinc the 
positive metal ; and hence a weaker current deposits more copper, in 
consequence of which the deposit becomes redder, while, vice versa, 
a more powerful current decomposes besides the copper solution 
also a larger quantity of zinc solution and reduces zinc, the color 
produced being more pale yellow to greenish. By bearing this 
in mind it is not difficult to obtain any desired shades within 
certain limits. 

I. Brass bath according to Roseleur. — Blue vitriol and zinc 
sulphate (white vitriol), of each 5J ounces, and crystallized car- 
bonate of soda, 15f ounces. — Crystallized carbonate of soda and 
crystallized bisulphide of soda, of each 7 ounces ; 98 per cent, 
potassium cyanide, 8f ounces ; arsenious acid, 30} grains ; water, 
10 quarts. 

The bath is prepared as follows : In 5 quarts of warm water 



DEPOSITION OF COPPER, BRASS, AND BRONZE. 193 

dissolve the blue vitriol and the zinc sulphate ; and in the other 
5 quarts the 15} ounces of carbonate of soda; then mix both 
solutions, with stirring. A precipitate of carbonate of copper 
and carbonate of zinc is formed, which is allowed quietly to settle 
for 10 to 12 hours, when the supernatant clear fluid is carefully 
poured off, so that nothing of the precipitate is lost. Washing 
the precipitate is not necessary ; the clear fluid poured off is of no 
value, and is thrown away. Now add to the precipitate so much 
water that the resulting fluid amounts to about 6 quarts, and dis- 
solve in it, with constant stirring, the carbonate and bisulphite 
of soda, adding these salts, however, not at once, but gradually, 
in small portions to avoid foaming over by the escaping carbonic 
acid. Dissolve the potassium in 4 quarts of cold water and add 
this solution, with the exception of about J pint, in which the 
arsenious acid is dissolved with the assistance of heat, to the first 
solution, and finally add. the solution of arsenious acid in the J 
pint of water retained, when the bath should be clear and colorless. 
If after continued stirring particles of the precipitate remain un- 
dissolved, carefully add somewhat more potassium cyanide until 
solution is complete. 

Fresh brass baths work, as a rule, more irregular than any 
other baths containing cyanide, the deposit being either too red 
or too green or gray, while frequently one side of the objects is 
coated quite well, and the other not at all. To force the bath to 
work correctly it must be thoroughly boiled, the water which is 
lost by evaporation being replaced by the addition of distilled 
water or pure rain water. If boiling is to be avoided, the bath, 
as previously mentioned, is worked through for hours, and even 
for days, with the current, until an object suspended in it is cor- 
rectly brassed. 

The addition of a small quantity of arsenious acid is claimed to 
make the brassing brighter ; but the above-mentioned proportion 
of 30} grains for a 10 quart bath must not be exceeded, as otherwise 
the color of the deposit would be too light, and show a gray tone. 

II. Crystallized carbonate of soda, JOJ ounces; crystallized 

bisulphite of soda, 7 ounces ; neutral acetate of copper, 4.4 ounces ; 

crystallized chloride of zinc, 4.4 ounces ; 98 per cent, potassium 

cyanide, 14.11 ounces ; arsenious acid, 30} grains ; water 10 quarts. 

13 



194 ELECTRO-DEPOSITION OF METALS. 

The preparation of this bath is more simple than that of the 
preceding. 

Dissolve the carbonate and bisulphite of soda in 4 quarts of 
water, then mix the acetate of copper and chloride of zinc with 
2 quarts of water, and gradually add this mixture to the solution 
of the soda salts. Next dissolve the potassium cyanide in 4 quarts 
of water and add this solution to the first, retaining, however, a 
small portion of it, in which dissolve the arsenious acid with the 
assistance of heat. Finally add the arsenious acid solution, when 
the bath will become clear. Boiling the bath, or working it 
through with the current, is also required. 

For brassing iron in this bath the addition of carbonate of soda 
may be increased up to 35 ounces for a 10 quart bath, this being 
also permissible, when frequent scratch brushing is to be avoided 
in coating zinc articles with a heavy deposit of brass ; because it 
seems that a large content of carbonate of soda in the bath con- 
siderably retards the changing of the brass color into a discolored 
brown, though the brilliancy of the deposit appears to suffer some- 
what. When boiled from 1 to 2 hours, or worked through with the 
current for 10 to 12 hours, the bath prepared according to formula 
II works very well ; it requires a current of 0.5 to 0.55 ampere, 
with a tension of 3.5 to 4 volts per 15J square inches surface. 

As previously mentioned, the color of the deposit depends on 
the proportional quantity in which copper and zinc are present, 
a strong current depositing more zinc and a weak current more 
copper. By diminishing or increasing the current-strength by 
means of the resistance board, a deposit of a redder or more pale 
yellow to greenish color can be produced. However, with a bath 
which does not contain copper and zinc in the correct proportional 
quantities, and especially with old baths long in use, a determined 
color of the deposit cannot be produced with the assistance of the 
resistance board. In such case the content of the metal lacking 
in the bath, which is required for the production of a determined 
color, must be augmented by the addition of solution of the re- 
spective metallic salt in potassium cyanide. 

Suppose a bath which originally contained copper and zinc 
salts in equal proportions has been long in daily use. Now, 
since brass contains more copper than zinc, it is evident that more 



ASS, AND BRONZE. 195 

of the former will be withdrawn from the bath than of the latter, 
and finally a limit will be reached when the bath with a current 
suitable for the decomposition of the solution will deposit a 
greenish or gray brass, and with a weaker current produce no 
deposit whatever. The only help in such a case is the addition 
of sufficient solution of cyanide of copper in potassium cyanide, 
so that, even with quite a powerful current, a deposit of a beauti- 
ful brass color is produced, the shades of which can then again 
be controlled with the help of the resistance board. However, 
it must not be forgotten that every addition of a metallic salt 
momentarily irritates the brass bath, making it, so to say, sick, 
and to confine this phenomenon to the narrowest limit an addition 
of carbonate and bisulphite of soda should at the same time be 
made, and the bath be worked through with the current as pre- 
viously described, until a test shows that it works in a regular 
manner. 

Annealed sheets of brass not rolled too hard, and of as nearly 
as possible the same composition and color the deposit is to show, 
are used as anodes. The anode-surface should be at least twice 
as large as that of the objects to be brassed, though it is best to 
use as many anodes as the anode-rods will hold. 

As in the copper bath an abundant formation of slime on the 
anodes indicates the want of potassium cyanide in the bath. In 
this case the evolution of gas bubbles on the objects is very 
slight, and the deposit forms slowly. This is remedied by an addi- 
tion of potassium cyanide. The sIoav formation of the deposit, 
however, may also be due to a want of metallic salts ; in this 
case not only potassium cyanide, but also solution of cyanide of 
copper and cyanide of zinc in potassium cyanide, has to be added. 
For this purpose prepare a concentrated solution of potassium 
cyanide in water, and a solution of equal parts of blue vitriol 
and zinc sulphate in w r ater. From the latter precipitate the 
copper and zinc as carbonates with a solution of carbonate of 
soda as given in formula I, p. 192. After allowing the precipitate 
to settle pour off the clear supernatant fluid and add to the preci- 
pitate, with vigorous stirring, of the potassium cyanide solution, 
until it is dissolved ; if heating takes place thereby, add from 
time to time a little cold water. Add this solution with a small 



196 ELECTRO-DEPOSITKXN OF METALS. 

excess of potassium cyanide, and the addition of carbonate or 
bisulphite of soda to the bath, and boil the latter or work it 
through with the current. A more simple method is to procure 
cyanide of copper and cyanide of zinc, or concentrated solutions 
of these combinations from a dealer in such articles. In the 
first case rub in a mortar equal parts of cyanide of zinc and 
cyanide of copper with water to a thickly fluid paste. Pour this 
paste into potassium cyanide solution, containing about 7 ozs. of 
potassium cyanide to the quart, as long as the metallic cyanides 
dissolve quite rapidly with stirring. When solution takes place 
but slowly, stop the addition of paste. 

When a brass bath contains too large an excess of potassium 
cyanide, a very vigorous evolution of gas takes place on the 
objects, but the deposit is formed slowly or not at all ; besides 
the deposit formed has the tendency of peeling off in scratch- 
brushing. In this case the injurious excess has to be removed, 
which is effected by pouring, with vigorous stirring, a quantity 
of the above-mentioned thinly fluid paste of cyanide of zinc and 
cyanide of copper into the bath. 

III. Crystallized carbonate of soda 10J ozs., crystallized bisul- 
phite of soda 7 ozs., cyanide of copper and cyanide of zinc of 
each 3 J ozs., water 10 quarts and 98 per cent, potassium cyanide 
until the solution is clear. 

To prepare the bath dissolve the carbonate and bisulphite of 
soda in 2 to 3 quarts of water, rub in a porcelain mortar the 
cyanide of copper and cyanide of zinc with 1 quart of water to 
a thin paste, add this paste to the solution of the soda salts and 
finally add, with vigorous stirring, concentrated potassium cyan- 
ide solution until the metallic cyanides are dissolved. Dilute the 
volume to 10 quarts, and, for the rest, proceed as given for formulae 
I and II. 

For brassing zinc exclusively, Roseleur recommends the follow- 
ing bath : — 

IY. Dissolve 9f ozs. of crystallized bisulphite of soda and 14 
ozs. of 70 per cent, potassium cyanide in 8 quarts of water ? and 
add to this solution one of 4f ozs. each of neutral acetate of copper 
and crystallized chloride of zinc, 5 J ozs. of aqua ammonia, and 2 
quarts of water. 



DEPOSITION OF COPPER, BRASS, AND BRONZE. 197 

For brassing cast-iron, wr ought-iron, and steel, Gore highly 
recommends the following composition : — 

V. Dissolve 35J ozs. of crystallized carbonate of soda, 7 ozs. 
of crystallized bisulphite of soda, 13J ozs. of 98 per cent, potas- 
sium cyanide in 8 quarts of water ; then add, with constant stir- 
ring, a solution of fused chloride of tin 3J ozs., and neutral acetate 
of copper 4J ozs., in 2 quarts of water. Boil and filter. This 
bath works best with a current of 3.75 volts. 

According to Morris and Johnson, a good brass bath is said to 
be obtained as follows : — 

"VI. Carbonate of ammonia 35J ozs., 70 per cent, potassium 
cyanide 35J ozs., cyanide of copper and cyanide of zinc, each 
2 J ozs., water 10 quarts. 

The large content of potassium cyanide in this bath is unin- 
telligible. 

A solution for transferring any copper zinc alloy serving as 
anode is composed, according to Hess, as follows : — 

VII. Bisulphite of soda 14} ozs., crystallized sal ammoniac 
9J ozs., 98 per cent, potassium cyanide 2J ozs., water 10 quarts. 

Cast metal plates are to be used as anodes. The transfer 
begins after a medium strong current has for a few hours passed 
through the bath. This bath is also well adapted for the depo- 
sition of tombac, with the use of tombac anodes ; and the most 
suitable tension of the current is 3 to 3.5 volts. 

Execution of brassing. — To avoid unnecessary repetition, we 
refer, as regards the practice of brassing, to what has been said 
under " Execution of Coppering," the manipulations being the 
same, while the treatment of the brass baths has already been 
sufficiently discussed in the preceding. 

The deposition of several metals from a common solution is 
not an easy task, and requires attention and experience ; if, how- 
ever, the directions given in this chapter are followed, the operator 
will be able to conduct, after short experience, the brassing pro- 
cess with the same success as one in which but one metal is 
deposited. 

In brassing, the distance of the objects to be brassed from the 
anodes is of considerable importance. If objects with deep depres- 
sions or high reliefs are hung in the brass bath, it will be found that, 



198 ELECTRO-DEPOSITION OE METALS. 

with the customary distance of 3f to 5f inches from the anodes, 
the brassing of the portions in relief nearest to the anodes will 
turn out of a lighter color than that of the depressed portions, 
which will show a redder deposit, the reason for this being that 
the current acts more strongly upon the portions in relief, and 
consequently deposits more zinc than the weaker current, which 
strikes the depressions. To equalize the difference, the objects 
have to be correspondingly further removed from the anodes with 
lamp-feet up to 9f inches, and even more, when a deposit of the 
same color will be everywhere formed. 

The brassing of unground iron castings is especially trouble- 
some, and in order to obtain a beautiful and clear deposit, the 
preliminary scratch-brushing has to be executed with special care; 
but even then the color of the brass deposit will sometimes be found 
to possess a disagreeable gray tone. This is very likely largely 
due to the quality of the iron itself, and it is advisable first to 
give the casting a thin coat of nickel or tin, upon which a deposit 
of brass of the usual brilliancy can be produced. In baths serv- 
ing for brassing iron articles, a large excess of potassium cyanide 
must be avoided ; it is, however, an advantage to increase the con- 
tent of carbonate of soda. 

Brassing by contact and dipping. — Some authors have given 
directions for brassing by contact, for instance, Bacco, Weil, and 
others, but the results obtained are so unsatisfactory, and the 
process so uncertain, that it is not necessary to enter into any 
further description. 

The inlaying with black of brassed articles is done in the same 
manner as described under " Coppering." 

For oxidizing, platinizing, and coloring of brass, see the proper 
chapter. 

3. Bronzing. 

The electrolytic coating of metallic objects with bronze, i. e., a 
copper-tin alloy or an alloy of copper tin and zinc, is but seldom 
practised, the bronze tone being in most cases imitated by a 
deposit of brass, with a somewhat larger content of copper. 

For coating wrought- and cast-iron with bronze, Gountier re- 
commends the following solution : — 



DEPOSITION OF COPPER, BRASS, AND BRONZE. 199 

Yellow prussiate of potash 10J ozs., cuprous chloride 5 J ozs., 
stannous chloride (tin salt) 14 ozs., sodium hyposulphite 14 ozs., 
water 10 quarts. 

According to Ruolz, a bronze bath is prepared as follows : 
Dissolve at 122° to 140° F., cyanide of copper 2.11 ozs., and 
oxide of tin 0.7 oz. in 10 quarts of potassium cyanide solution 
of 4° Be. The solution is to be filtered. 

Eisner prepares a bronze bath by dissolving 21 ozs. of blue 
vitriol iu 10 quarts of water, and adding a solution of 2 J ozs. of 
chloride of tin in potash lye. 

Salzede recommends the following bath, which is to be used at 
between 86° and 95° F. : Potassium cyanide 3J ozs., carbonate 
of potash 35J ozs., stannous chloride (tin salt) 0.42 oz., cuprous 
chloride J oz., water 10 quarts. 

Weil and Newton claim to obtain beautiful bronze deposits 
from solutions of the double tartrate of copper and potash, and 
the double tartrate of the protoxide of tin and potash, with 
caustic potash, but fail to state the proportions. 

The above formulae are here given with all reserve, since ex- 
periments with them failed to give satisfactory results ; with 
Gountier's, Ruolz's and Eisner's baths no deposit was obtained but 
only a strong evolution of hydrogen, while even with a strong 
current Salzede's bath did not yield a bronze deposit, but simply 
one of tin. The following method of preparing a bronze bath 
may be recommended : Prepare, each by itself, solutions of phos- 
phate of copper and stannous chloride (tin salt) in sodium pyro- 
phosphate. From a blue vitriol solution precipitate, with sodium 
phosphate, phosphate of copper, allow the latter to settle and 
after pouring off the clear supernatant fluid, bring it to solution 
by concentrated solution of sodium pyrophosphate. On the other 
hand, add to a saturated solution of sodium pyrophosphate 
solution of tin salt as long as the milky precipitate formed 
dissolves. Of these two metallic solutions add to a solution of 
sodium pyrophosphate, which contains about If ozs. of the salt to 
the quart, until the precipitate appears quickly and of the desired 
color. For anodes, use cast bronze plates, which dissolve well in 
the bath. Some sodium phosphate has from time to time to be 
added to the bath, and if the color becomes too light, solution of 
copper, and, if too dark, solution of tin. 



200 ELECTRO-DEPOSITION OF METALS. 

For deposits of tombac Hess's bath (formula VII, brassing) 
with anodes of plate or sheet tombac can be recommended ; 3 to 
3.5 volts being the most suitable tension of the current for the 
decomposition of the bath. 

For nickel-bronze, see p. 177. 

The execution of bronzing requires the same attention and 
manipulations as those given for brassing. 



CHAPTER IX. 

DEPOSITION OF SILVER. 

Properties of silver. — Pure silver is the whitest of all known 
metals ; it takes a fine polish , is softer and less tenacious than 
copper, but harder and more tenacious than gold. It is very 
malleable and ductile, and can be obtained in exceedingly 
thin leaves and fine wire. Its specific gravity is 10.48 to 10.5, 
according to whether it is cast or hammered. It melts at about 
1832° F. It is unacted upon by the air, but in the atmosphere 
of towns it gradually becomes coated with a film of silver sul- 
phide. It is rapidly dissolved by nitric acid, nitrogen dioxide 
being evolved ; hydrochloric acid has but little action upon it 
even at boiling heat; when heated with concentrated sulphuric 
acid it yields sulphur dioxide and silver sulphate. 

Silver baths. — Only formulae for approved baths will be given. 

Silver bath for a heavy electro-deposit of silver (silvering by weight). 
I. 98 per cent, potassium cyanide 14 ozs., fine silver as silver 
chloride 8} ozs., distilled water 10 quarts. 

la. 98 per cent, potassium cyanide 8f ozs., fine silver as silver 
cyanide 8f ozs., distilled water 10 quarts. 

Before describing the preparation of the bath a few words may 
be said in regard to the old dispute whether it is preferable to use 
silver cyanide or silver chloride. Without touching upon all the 
arguments advanced, it may be asserted by reason of conscientious 
comparative experiments, that the results are the same and that 
the life of the baths is also the same whether one or the other salt 



DEPOSITION OF SILVEK. 201 

has been used in the original preparation. From a theoretical 
standpoint, silver cyanide must be given the preference ; but as 
the disadvantages in respect to the life of the bath ascribed by 
some to silver chloride do not exist, it might be advisable for 
those who prepare their own baths to use silver chloride. 

Preparation of bath I with silver chloride. — Dissolve 14 ozs. of 
chemically pure nitrate of silver, best the crystallized and not the 
fused article, in 5 quarts of water, and add to the solution pure 
hydrochloric acid or common salt solution, with vigorous stirring 
or shaking, until a sample of the fluid filtered through a paper 
filter forms no longer a white caseous precipitate of silver chloride 
when compounded with a drop of hydrochloric acid. These, as 
well as the succeeding operations until the silver chloride is com- 
plete, have to be performed in a darkened room, as silver chloride 
is partially decomposed by light. Now separate the precipitate 
of silver chloride from the solution by filtering, using best a large 
bag of close felt, and wash the precipitate in the felt bag with 
fresh water. Continue the washing until blue litmus paper is no 
longer reddened by the wash water, if hydrochloric acid was used 
for precipitating, or, if common salt solution was used, until a small 
quantity of the wash water on being mixed with a drop of lunar 
caustic solution produces only a slight milky turbidity and no pre- 
cipitate. Now bring the washed silver chloride in portions from 
the felt bag into a porcelain mortar, rub it with water to a thin paste 
and pour the latter into the potassium cyanide solution consisting 
of 14 ozs. of 98 per cent, potassium cyanide in 5 quarts of water, 
in which, with vigorous stirriug, the silver chloride gradually dis- 
solves. All the precipitated silver chloride having been brought 
into solution, dilute with water to 10 quarts of fluid and boil the 
bath, if possible, for one hour, replacing the water lost by evapo- 
ration. A small quantity of black sediment containing silver 
thereby separates from which the colorless fluid is filtered off. 
The sediment is added to the silver residues and is worked together 
with them for the recovery of the silver by one of the methods to 
be described later on. 

Preparation of bath la with silver cyanide. — Dissolve 14 ounces 
of chemically pure crystallized nitrate of silver in 5 quarts of 
water, and precipitate the silver with prussic acid, adding the 



202 ELECTRO-DEPOSITION OF METALS. 

latter until no more precipitate is produced by the addition of a few 
drops of prussic acid to a filtered sample of the fluid. Now 
filter, wash out and proceed for the rest exactly as stated for the 
bath with silver chloride, except that only 8f ounces of potassium 
cyanide are taken for dissolving the silver cyanide. In working 
with prussic acid avoid inhaling the vapor which escapes from 
the liquid prussic acid, especially in the warm season of the year ; 
and be careful the acid does not come in contact with cuts on the 
hands. It is one of the most rapidly acting poisons. 

Cyanide of silver may also be prepared as follows : Dissolve 
14 ounces of chemically pure crystallized nitrate of silver in 5 
quarts of water, and add moderately concentrated potassium 
cyanide solution until no more precipitate is formed, avoiding, 
however, an excess of the precipitating agent, as it would again 
dissolve a portion of the cyanide of silver. The precipitated 
cyanide of silver is filtered off, washed and dissolved in potassium 
cyanide, as above described. 

The bath prepared according to formula I or la, serves chiefly 
for thickly silvering objects of German silver; it may, however, 
be used for silvering other metals by weight. 

Silver bath for ordinary electro-silvering. — II. 98 per cent, 
potassium cyanide 6 \ to 7 ounces, fine silver (as silver nitrate or 
chloride), 3 J ounces ; distilled water, 10 quarts. 

To prepare the bath dissolve 5 J ounces of chemically pure 
crystallized nitrate of silver in 5 quarts of distilled water ; in the 
other 5 quarts of water dissolve the potassium cyanide, and mix 
both solutions. Or, if chloride of silver is to be used, precipitate 
the solution of 3J ounces of the silver salt in the same manner as 
given for formula I. ; wash the precipitated chloride of silver, 
and dissolve it in the potassium cyanide solution. 

Vats of stone-ware, enamelled iron, or lined with ebonite mass 
are to be used for the silver baths. 

Treatment of the silver baths ; silver anodes. — Frequently the 
error is committed of adding too much potassium cyanide to the 
baths. A certain excess of it must be present and is taken into 
consideration in the formulae given. For dissolving the cyanide 
of silver prepared from 14 ounces of nitrate of silver, as given 
in formula la, only about 5J ounces of potassium cyanide are 



DEPOSITION OF SILVER. 203 

required, and the consequence of working with such a bath devoid 
of all excess would be that, on the one hand, the bath would offer 
a considerable resistance to the current, and on the other, that the 
deposit of silver would not be uniform and homogeneous. Hence 
with the use of a medium strong current about 30 to 35 per cent, 
more of potassium cyanide than fine silver is taken. In working 
with a stronger current, this excess would, however, be too large, 
in consequence of which the deposit would not adhere properly 
and peel off in scratch-brushing. And again, with a weak cur- 
rent the baths can, without disadvantage, stand a larger excess. 
As a rule, however, the proportion between fine silver and potas- 
sium cyanide in the above formula may be considered as normal, 
and the current-strength will have to be regulated so that a de- 
posit of fine structure which adheres firmly is formed. The most 
suitable current-strength per 15 J square inches of surface is 0.25 
to 0.15 ampere, and 0.5 to 0.75 volt tension ; the tension of a 
Daniell element being more than sufficient for the decomposition 
of the silver bath. On account of the silver bath requiring a 
current of slight electro-motive force, the Smee element, which 
yields 0.48 volt, is much liked for silvering in this country and 
in England. The Bunsen element may, how r ever, also be used if 
the surface to be silvered is made to correspond with the energy 
of such an element ; or, what is advisable in all cases, if a resist- 
ance board is placed in the circuit. On account of the slight 
tension required in silvering larger surfaces of objects, the ele- 
ments are not to be coupled one after the other for tension, but 
alongside one another for quantity. In no case must an evolution 
of hydrogen be perceptible on the articles, and the current must 
be more weakened the larger the excess of potassium cyanide in 
the bath. 

Whether too much, or not enough, potassium cyanide is present 
in the bath is indicated by the appearance of the silvered objects 
and the properties of the deposit, as well as by the behavior of 
the anodes in the bath during and after silvering. 

It may be accepted as a rule that with a moderate current the 
objects must in the course of 10 to 15 minutes be coated w 7 ith a 
thin, dull white film of silver. If this be not the case and the 
film of silver shows a meagre bluish-white tone, potassium cyan- 



204 ELECTRO-DEPOSITION OF METALS. 

ide is wanting. However, if, on the other hand, the dull white 
deposit forms within 2 to 3 minutes, and shows a crystalline 
structure, or a dark tone playing into gray-black, the content of 
potassium cyanide in the bath is too large, provided the current 
is not excessively strong. If copper .and brass become coated 
with silver without the assistance of the current, the bath con- 
tains also too much potassium cyanide. 

In silvering, even if the objects are to be but thinly coated, 
insoluble platinum anodes should never be used, but only anodes 
of fine silver, which are capable of keeping the content of silver 
in the bath quite constant. From the behavior and appearance 
of the anodes, a conclusion may also be drawn as to whether the 
content of potassium cyanide in the bath is too large or too small. 
If the anodes remain silver-white during silvering, it is a sure 
sign that the bath contains, certainly, more potassium cyanide than 
is necessary and desirable ; but if they turn gray or blackish, and 
retain this color after silvering when no current is introduced into 
the bath for a quarter of an hour or more, potassium cyanide is 
wanting. On the other hand, the correct content of potassium 
cyanide is present when the anodes acquire during the silvering 
process a gray tone, which, after the interruption of the current, 
gradually changes back to a pure white. 

Potassium cyanide when found wanting should be quickly 
added, though never more than 30 to 37 J grains per quart of the 
bath at one time, so as to avoid going to the other extreme. Too 
large a content of potassium cyanide is remedied by adding to the 
bath, with constant stirring, a small quantity of cyanide or chlo- 
ride of silver rubbed with water to a thinly-fluid paste, whereby 
the excess is rendered harmless in consequence of the formation 
of the double salt of silver cyanide and potassium. Instead of 
such addition the current may, however, also be used as a corrector 
of the excess. For this purpose suspend as many silver anodes 
as possible to the anode-rods, but only a single anode as an object 
to the object-rod, and allow the current to pass for a few hours 
through the bath, whereby the excess of potassium cyanide is ren- 
dered innoxious by the dissolving silver. 

The bath can be kept quite constant by silver anodes provided 
potassium cyanide be regularly added at certain intervals, and the 



DEPOSITION OF SILVER. 205 

anode-surface is equal to that of the objects to be silvered. But 
since, on account of the expense, a relatively small anode-surface 
is frequently used, the content of silver in a bath continuously 
worked will finally become lower, and augmentation, by the addi- 
tion of silver, will be required. The manner of effecting this 
augmentation depends on whether the baths are used for silvering 
by weight or for lighter silvering, or whether the baths are worked 
without stopping from morning till evening. If the content of 
silver in baths I and la is not to be augmented by the current 
itself, it is best to use exclusively solution of silver cyanide in 
potassium cyanide. If, however, the working of such a bath can 
for some time be interrupted, then add not too small a quantity 
of potassium cyanide to the bath, and, after hanging a small 
silver anode on the object-rod and a sufficient number of anodes 
on the anode-rods, dissolve with not too weak a current silver 
from the anodes until the latter, which at first remain white, 
begin to acquire a gray tone. Silver is, of course, deposited upon 
the anode suspended as an object, which is, however, not lost, it 
being dissolved later on when the anode is secured to the anode- 
rod. The quantity of silver dissolved 'is considerably larger than 
that deposited upon the small anode-surface suspended as an object. 
It has previously been mentioned that with proper treatment 
baths made with chloride of silver have the same duration of life 
as those prepared with cyanide of silver. The chief feature of 
such proper treatment is the augmentation of the content of silver 
by electrolysis, i. e., by the current itself. If it were not possible 
to proceed in this manner, the bath, by the frequently repeated 
additions of solution of the chloride, instead of the cyanide of 
silver in potassium cyanide, would gradually thicken by reason 
of the potassium chloride which is thereby simultaneously intro- 
duced, and in consequence of this would offer greater resistance 
to the current. The fear expressed by some that a crystalline 
separation of potassium chloride, and the consequent formation of 
a porous deposit upon the objects, might take place is erroneous, 
potassium chloride being one of the most soluble salts and show- 
ing but little tendency to separate in crystals from aqueous solu- 
tions. The above-mentioned gradual thickening is, however, a 
disadvantage which shows itself by the deposit being less homo- 



206 ELECTEO-DEPOSITION OF METALS. 

geneous, and for this reason it is advisable, when silvering by 
weight to use silver cyanide instead of the chloride for strength- 
ening the silver bath. 

A gradual thickening of the bath may also take place if potas- 
sium cyanide containing potash is used instead of the preparation 
free from potash, and of 98 to 99 per cent, purity. Even pure 
fused potassium cyanide produces a thickening of the bath, 
which, however, progresses very slowly. This thickening is due 
to a portion of the excess of potassium cyanide being converted 
by the action of the air into potassium carbonate. The latter thus 
formed must from time to time be neutralized, which is mostly 
done with prussic acid, the potassium carbonate being thereby 
converted into potassium cyanide. Instead of prussic acid, cal- 
cium cyanide or barium cyanide may be added, as long as a pre- 
cipitate of calcium carbonate or barium carbonate is formed ; the 
clear solution is to be separated from the precipitate by filtering. 

For augmenting the content of silver in baths prepared accord- 
ing to formula II, solution of nitrate of silver or of chloride of 
silver in potassium cyanide, may unhesitatingly be used, since the 
thickening proceeds more slowly on account of the smaller con- 
tent of salt in the bath, and because a cheaper bath can be more 
readily renewed without the sacrifice of money than one for heavy 
silvering. The recovery of silver from old baths is effected by 
one of the methods given later on. 

To determine whether the bath contains silver and excess of 
potassium cyanide in proper proportions, the following method 
may be used: Dissolve 1 gramme (15.43 grains) of chemically 
pure crystallized nitrate of silver in 20 grammes (0.7 oz.) of 
water, and gradually add this solution, with constant stirring 
with a glass rod, to 100 grammes (3.52 ozs.) of the silver bath 
in a beaker glass, as long as the precipitate of silver cyanide 
formed dissolves by itself. If, after adding the entire quantity 
of silver solution, the precipitate dissolves rapidly, too large an 
excess of potassium cyanide is present in the bath, and vice versa, 
if the precipitate does' not completely dissolve after stirring, 
potassium cyanide is wanting. 

While this experiment allows us to judge of the proportion of 
silver to potassium cyanide, it does not throw any light upon the 



DEPOSITION OF SILVER. 207 

effective content of silver in the bath, and for refreshing the latter, 
it is desirable to know the actual content of silver in it. To 
determine this, mix 25 cubic centimetres of the silver bath in 
a beaker glass with 50 cubic centimetres of pure hydrochloric 
acid and 50 cubic centimetres of water, and heat upon a water 
or sand bath until all odor of prussic acid has disappeared, 
and then dilute with 200 cubic centimetres of water. Filter off 
the precipitate of chloride of silver formed through a weighed 
filter, dried at 212° F., wash the precipitate with hot distilled 
water until the filtrate is no longer rendered turbid by a drop 
of silver solution (1 part of nitrate of silver to 20 of water), and 
dry at 212° F. until the weight remains constant. After deduct- 
ing the weight of the dried filter, the weight of the precipitated 
chloride of silver is obtained, and from this the weight of the 
metallic silver is calculated according to the following formula : — 

143.5 : 108 = grammes of chloride of silver found : x. 

The content of silver in the bath per liter is then found by 
multiplying x by 40. 

In silvering, the constant agitation of the layers of fluid is of 
decided advantage, streaks being otherwise readily formed upon 
the silvered objects. To keep the articles in gentle motion while 
in the bath, one method is to connect the suspending rods to a 
frame of iron having four wheels, about 3 inches in diameter, 
connected to it, which slowly travel to and fro to the extent of 
3 or 4 inches upon inclined rails attached to the upper edges of 
the tank, the motion, which is both horizontal and vertical, being 
given by means of an eccentric wheel driven by steam power. 
By another arrangement, the frame supporting the articles does 
not rest upon the vat, but is suspended above the bath, and 
receives a slow swinging motion from a small eccentric or its 
equivalent. In the Elkington establishment at Birmingham, the 
following arrangement is in use : All the suspending rods of the 
bath rest upon a copper mounting, which, by each revolution of 
an eccentric wheel, is lifted about { inch, and then returned to its 
position ; the copper mounting is connected to the main negative 
wire of the dynamo-machine by a copper cable. The same object 
may also be attained by giving the objects a horizontal instead of 



208 



ELECTRO-DEPOSITION OF METALS. 



vertical motion, as shown in Fig. 80, in which the motion is pro- 
duced by an eccentric wheel on the side. 



Fig. 80. 




Finally it remains to mention a singular phenomenon in silver- 
ing which has not yet been explained. A small addition of certain, 
and especially of organic substances, which, however, must not 
be made suddenly or in too large quantities, produces a fuller and 
better adhering deposit of greater lustre than can be produced in 
fresh baths. Elkington observed that an addition of a few drops 
of carbon-bisulphide to the bath made the silvering more lustrous, 
while others claim to have used with success solutions of iodine 
in chloroform, of gutta percha in chloroform, as well as heavy 
hydrocarbons, tar oils, etc. However, many baths have been en- 
tirely spoiled by an attempt to change them into bright working 
baths by the addition of such ingredients ; and hence it is best to 
leave such experiments alone. There is no doubt that a silver 
bath becomes better in the degree as it takes up small quantities 
of organic substances from dust and air. Fresh silver baths will 
more rapidly accommodate themselves to regular working by the 
addition of a few drops of spirit of sal ammoniac. 

After silvering the objects frequently show, instead of a pure 
white, a yellow tone or they become yellow in the air, which is 
ascribed to the formation of basic silver salts in the deposit. To 



DEPOSITION OF SILVER. 209 

overcome this evil it has been proposed to allow the objects to 
remain in the bath for a few minutes after interrupting the cur- 
rent, whereby the basic salts are dissolved by the potassium cyan- 
ide of the bath ; or the same object is attained by inverting the 
electrodes for a few seconds, after plating, thus transforming the 
articles into anodes. The electric current carries away the basic 
salt of silver in preference to the metal. This operation should, 
of course, not be prolonged, otherwise the silver will be entirely 
removed from the objects, and will be deposited on the anodes. 
For the same purpose some electro-platers hold in readiness a 
warm solution of potassium cyanide, in which they immerse the 
silvered articles for half a minute. 

Execution of silvering. — A. Silvering by weight. — Copper, brass 
and all other copper alloys may be directly silvered after amalga- 
mating (quicking), whilst iron, steel, nickel, zinc, tin, lead and 
Britannia are first coppered or brassed, and then amalgamated. 

The mechanical and chemical preparation of the objects for the 
silvering process is the same as described on pages 119 and 
125. To obtain well-adhering deposits great care must be exer- 
cised in freeing the objects from grease and in pickling. As a 
rule, objects to be silvered are ground and polished ; but the latter 
must not be carried too far, since the deposit of silver does not 
adhere well to highly polished surfaces ; and, in case such highly 
polished objects are to be silvered, it is best to deprive them of 
their smoothness by rubbing with pumice powder, emery, etc., or 
by pickling. 

The treatment of copper and its alloys, German silver and 
brass, which have chiefly to be considered in silvering by weight, 
is, therefore, as follows : — 

1. Freeing from grease by hot potash or soda lye (1 part of 
caustic alkali to 8 or 10 parts of water), or by brushing with the 
lime paste mentioned on page 125. 

2. Pickling in a mixture of 1 part, by weight, of sulphuric 
acid of 66° Be. and 10 of water. This pickling is only required 
for rough surfaces of castings, ground articles being immediately 
after freeing from grease treated according to 3. 

3. Rubbing with a piece of cloth dipped in fine pumice powder 
or emery, after which the powder is to be removed by washing. 

14 



210 ELECTRO-DEPOSITION OF METALS. 

4. Pickling in the preliminary pickle rinsing in hot water and 
quickly drawing through the bright-dipping bath (page 1 20), and 
again thoroughly rinsing in several waters. 

5. Amalgamating (quicking) by immersion in a solution of 
mercury, called the quicking solution, and consisting of a solu- 
tion of 0.35 ounce of nitrate of mercury in 1 quart of water, to 
which, with constant stirring, pure nitric acid in small portions 
is added, until a clear fluid results; a weak solution of potassium- 
mercury cyanide in water is, however, preferable for quicking. 

6. In the quicking solution the objects remain only long enough 
to acquire a uniform white coating, when they are rinsed in clean 
water, and gone over with a brush in case the quicking shows a 
gray instead of a white tone. 

The objects are now brought into the silver bath and secured 
to the suspension rods by slinging wires of copper. For forks and 
spoons these wires are bent on their extremities in 
Fig. 81. such a manner that the fork or spoon may readily 
be inserted or removed. Fig. 81 presents this ter- 
minal hook. The straight portion of these wires 
which dips into the liquid is covered with a small 
tube of India rubber or coated with ebonite mass, 
which prevents the useless deposit of silver upon it. 
The hooped portions, however, become coated with 
silver, which may be removed by the use of acids 
after having raised the India rubber tube. 
Introduce at first a somewhat more powerful cur- 
rent into the bath so that the first deposit of silver takes place 
quite rapidly, and after 3 minutes regulate the current so that in 
10 to 15 minutes the objects are coated with a thin, dull film of 
silver. At this stage take them from the bath, and after seeing 
that all portions are uniformly coated with silver, scratch-brush 
them with a brass brush, which should, however, not be too fine. 
In doing this the deposit must not raise up ; if at this stage the 
objects stand thorough scratch-brushing, raising of the deposit in 
burnishing later on need not be feared. 

Any places which show no deposit of silver are vigorously 
scratch-brushed with the use of pulverized tartar, then again 
carefully cleansed by brushing with lime paste to remove any im- 




DEPOSITION OF SILVER. 211 

purities due to touching with the hands, pickled by dipping in 
potassium cyanide solution, rinsed off again, quicked and after 
careful rinsing returned to the bath. Special care must be had 
not to contaminate the bath with quicking solution, as this would 
soon spoil it. 

The objects now remain in the bath until the deposit has ac- 
quired a weight corresponding to the desired thickness. Knives, 
forks, and spoons receive a deposit of 2.11 to 3.52 ozs. of silver 
per dozen, such deposit being produced with elements in 10 to 14 
hours, and with a dynamo-electrical machine in 4 to 5 hours. 
According to Dr. William H. Wahl, the amount of silver depos- 
ited upon the several grades of plated table ware manufactured by 
the William Rogers Manufacturing Co., of Hartford, Conn., is 
as follows : — 

Per gross. Extra plate. Double plate. Triple plate. 

Teaspoons . . . .48 dwts. 4 ozs. 6 ozs. 

Dessertspoonsand forks . 72 " 6 " 9 " 

Tablespoons and rned. forks 96 " 8 " 12 " 

In order to control the weight of the deposit proceed as fol- 
lows : After having removed one of the pans of a sensitive beam 
balance, substitute for it a brass rod which keeps the other pan in 
equilibrium. Under this rod place a vessel filled with pure water 
and of sufficient diameter and depth to allow of the article sus- 
pended to the rod dipping entirely into the water without touch- 
ing the sides of the vessel. Suppose now that several dozen 
spoons of the same size and shape are at the same time to be 
provided with a deposit of a determined weight, it suffices to 
control the weight of the deposit of a single spoon, and when this 
has acquired the necessary deposit all the other spoons will also 
be coated with a deposit of silver of the same thickness as the test 
spoon. After the quicking and carefully rinsing of the spoons 
one of them is suspended to the brass rod of the balance so that 
it dips entirely under water ; the equilibrium is then re-established 
by placing lead shot upon the pan of the scale, and adding the 
weight corresponding to the deposit the spoon is to receive. Now 
bring the weighed spoon together with the rest into the bath, and 
proceed with the silvering process in the ordinary manner. After 
some time the weighed spoon is taken from the bath, rinsed in 



212 



ELECTEO-DEPOSITION OF METALS. 



water and hung to the brass rod of the scale ; if it does not 
restore the equilibrium of the latter, it is returned to the bath, 
again after some time weighed, and so on until its weight corre- 
sponds to that of the lead shot and weight placed in the pan of 
the scale, when it is assumed that the balance of the articles have 
also received their proper quantity and that the operation is com- 
plete. 

A more complete weighing apparatus is the plating balance 
first used by Brandely and later on improved by Roseleur. The 
apparatus, which is shown in Fig. 82, is designed for obtaining 

Fig. 82. 




deposits of silver " without supervision and with constant accu- 
racy, and which spontaneously breaks the current when the opera- 



DEPOSITION OF SILVER. 



213 



Fie. 83. 



tion is terminated." It is manufactured in various sizes suitable 
for small or large operations. 

It consists of: 1. A wooden vat, the upper edge of which 
carries a brass winding rod having a binding screw at one end to 
receive the positive conducting wire of the battery ; from this rod 
the anodes are suspended which are entirely immersed in the solu- 
tion, and communicate with cross brass rods by means of platinum 
wire hooks. These cross rods are flattened at their ends so that 
they may not roll and at the same time have a better contact with 
the " winding rod." 2. A cast-iron column screwed at its base to 
the side of the vat, and which carries near the top two projecting 
arms of cast-iron, the extremities of which are vertical and forked 
and may be opened or closed by iron clamps. These forks are 
intended for sustaining the beam and preventing the knives from 
leaving their bearings under the influence of too 
violent oscillations. In the middle of the two 
arms are two wedge-shaped recesses of polished 
steel to receive the knife edges of the beam. 
One of the arms of the column carries at its 
end a horizontal ring of iron in which is fixed 
a heavy glass tube supporting a cup of polished 
iron which is insulated from the column (Fig. 
83). 

This cup has at its lower part a small pocket 
of lamb-skin or of India rubber which by means 
of a screw beneath may be raised or lowered. 
This flexible bottom allows the operator to 
lower or raise at will, the level of the mer- 
cury introduced afterwards into the iron cup. 
Another (lateral screw) permits connection to be 
made with the negative electrode. 3. A cast-iron beam carrying 
in the middle two sharp knife edges of the best steel hardened 
and polished. At each extremity there are two parallel bearings 
of steel separated by a notch, and intended for the knife edges of 
the scale pan that receives the weights, and those of the frame 
supporting the articles to be silvered. One of the arms of the 
beam is provided with a stout platinum wire, placed immediately 
above and in the centre of the cup of mercury. According as 




214 



ELECTRO-DEPOSITION OF METALS. 



the beam inclines one way or the other, this wire plays in or out 
of the cup. 4. A scale pan for weights, with two knife edges of 
cast steel, which is attached to four chains supporting a wooden 
pan for the reception of weights. A smaller pan above is intended 
for the weights corresponding to that of the silver to be deposited. 
5. The frame for supporting the articles to be silvered, which is 
also suspended from two steel knife edges, and the rod of which 
is formed of a stout brass tube attached below to the brass frame 
proper, which last is equal in dimensions to the opening of the 
vat, and supports the rods to which the articles are suspended. 

Fig. 84. 




Fig. 84 shows a Roseleur plating balance, together with the 
resistance board, voltmeter and silver bath ; and will be understood 
without further explanation. 



DEPOSITION OF SILVER. 215 

For calculating the weight of the deposit from the density of 
current, see " Chemical and Electric Equivalents." 

When the articles have received a deposit of the required 
weight, they are treated for the prevention of subsequent yellow- 
ing according to one of the methods given on p. 208, than scratch- 
brushed with the use of decoction of soap root, plunged in hot 
water and dried in sawdust. 

Articles which are to retain the beautiful crystalline dead white 
with which they come from the bath are, without touching them 
with the fingers or knocking them against the sides of the vessel, 
plunged into very hot clean water and then suspended free to 
dry ; immediately after drying they are to be coated with a thinly- 
fluid lacquer to protect the dead white coating which readily 
turns yellow, and, moreover, is very sensitive. 

The silvered articles having been scratch -brushed, must finally 
be polished, which may be effected upon fine felt disks with the 
use of rouge, but imparting high lustre by burnishing is to be 
preferred, the deposit being first treated with the steel burnisher 
and then with the stone burnisher, as explained on p. 118. The 
steel burnisher consists of a piece of polished steel varying in 
shape mounted in a wooden handle. The operation of burnish- 
ing is very simple. Take hold of the tool very near to the steel 
or stone, and lean very hard with it on those parts which are to 
be burnished, causing it to glide by a backward and forward 
movement without taking it from the piece. When it is requisite 
that the hand should pass over a large surface at once, without 
losing its point of support on the work-bench, in taking hold of 
the burnisher be careful to place it just underneath the little finger. 
By these means the work is done more quickly, and the tool is 
more solidly fixed in the hand. During the whole process the 
tool must be continually moistened with black soap-suds. 

In some establishments in which plated table-ware in large 
quantity is turned out, ingeniously devised burnishing machines 
driven by power are in use, by which much of the manual labor 
is spared. The knife, spoon, etc., each supported by its tips in a 
suitable holder, are slowly rotated, while the burnishing tool 
moves quickly over the surface, performing the work rapidly and 
satisfactorily. 



216 ELECTRO-DEPOSITION OF METALS. 

"When the burnishing is completed, the surface is wiped off 
longitudinally with an old, soft calico rag ; sawdust, hard cloth, 
and tissue paper produce streaks. 

B. Ordinary silvering. — The operations the objects have to 
undergo, which are to receive a deposit of less thickness, are ex- 
actly the same as those described under silvering by weight, the 
only difference being that for quicking a weaker solution (15 to 
31 grains of nitrate of mercury to 1 quart of water) or very dilute 
solution of potassium-mercury cyanide is used, and that the 
objects remain in the bath for a shorter time. As previously 
mentioned, iron, steel, zinc, tin, etc., must previously be coppered 
or brassed ; however, tin and its alloys may also be directly 
silvered in the silver bath, but a larger excess of potassium 
cyanide is required than for copper, brass, or German silver. 

According to Dr. William H. Wahl, in the United States, the 
practice of previous coppering is not adopted either with Bri- 
tannia metal or steel. The practice of different establishments of 
cleansing their work differs somewhat, but all aim at the same 
result, viz., to secure a smooth adhering coating of metal upon 
an inferior base. 

The practice of the Meriden Britannia Co. ? s works at Meriden, 
Conn., as observed by Dr. William H. Wahl, is substantially as 
follows: With Britannia or " white metal:" The article is first 
cleansed of all grease by immersion in boiling alkali ; then into 
dilute muriatic acid ; then into a " striking" solution, viz., a weak 
cyanide of silver solution with a large proportion of free cyanide 
of potassium, and a large silver anode operated with a very strong 
electric current. The purpose of immersion in this solution is to 
effect an instantaneous deposit of silver on the metal, to better 
insure a perfect coating in the silver bath proper. The articles 
remain in the " striking" solution for a few seconds only, as its 
action, owing to the large proportion of free cyanide it contains, 
is very prompt, and as soon as they have received a thin coating, 
which takes place almost immediately, they are removed to the 
electro-plating bath, where they remain until they have received 
the proper coating of silver. In many cases, especially with 
articles of considerable size, cleansing in boiling alkali must be 
supplemented by scratch-brushing, in which case the acid dip may 



DEPOSITION OF SILVER. 217 

be dispensed with, and the article, after thorough rinsing and 
dipping in alkali to remove finger-marks, is immersed at once in 
the "striking" solution. 

German silver or nickel articles are first cleansed in boiling 
alkali, washed, then dipped in a mixture of two-thirds sulphuric 
and nitric acids, then into quicking solution, then into the 
" striking" solution, and from this into the plating bath. 

Steel articles are cleansed in boiling alkali, rinsed, dipped in 
muriatic acid, then in the " striking" solution, and from this into 
the plating bath. In case the articles require scouring the acid 
dip is dispensed with. For steel two " striking" solutions are 
used, one somewhat richer in silver than the other, the weaker 
solution being used first. 

In the William Rogers Manufacturing Co., Hartford, Conn., 
the following is the general outline of the methods in use for pre- 
paring work for plating : — 

For cleansing steel (cutlery). — Immersion in boiling alkali for the 
removal of grease ; scouring ; rinsing ; dipping into strong muri- 
atic acid ; then for a few seconds in a silver " striking" solution ; 
then in a plating bath until the required amount of silver is 
deposited. 

The formula for the " striking" solution which will be given 
later on is low in silver, rich in cyanide, and worked with a strong 
current and silver anode. 

Nickel-silver (German silver) for spoons. — Immerse in boiling 
alkali ; scouring, if necessary ; rinsing in water ; immersion in 
acid mixture, composed of two-thirds sulphuric acid and one-third 
nitric acid ; dipping in weak quicking solution (either very dilute 
potassium-mercury cyanide or acidulated nitrate of mercury); 
immersion for a few seconds in the silver " striking" solution ; 
and from this into the plating bath. 

Britannia metal (hollow-ware). — Cleansing in alkali as above ; 
rinsing in water; again immersing in alkali to remove finger- 
marks, if necessary , immersing in the " striking" solution, and 
from this into the plating solution. A quicking solution for 
Britannia, sometimes employed, is composed of a strong solution 
of sal ammoniac and corrosive sublimate, into which the articles 
are dipped after cleansing in potash. 



218 ELECTRO-DEPOSITION OF METALS. 

The silver " striking" solution, as used by the Wm. Eogers 
Manufacturing Co., of Hartford, Conn., is composed as follows : — 

Rogers's "striking" solution. — Cyanide of potassium 6 ozs., 
silver J oz., water 1 gallon. Use a strong current. 

Meriden Company's " striking solution." — Cyanide of potassium 
12 to 16 ozs., silver 8 to 10 dwts., water 1 gallon. 

The plating solution commonly employed by the Wm. Rogers 
Manufacturing Co. has the following composition : Cyanide of 
potassium 6 ozs., silver (in chlorate) 4 ozs., water 1 gallon. 

The usual formula of the Meriden Britannia Co. has the fol- 
lowing proportions: Cyanide of potassium 12 ozs., silver 3 ozs., 
water 1 gallon. 

In order to secure an extra heavy coating of silver on the con- 
vex surfaces of spoons and forks, which, being subject to greater 
wear than the other parts, require extra protection, the Meriden 
Britannia Co. uses a frame in which the articles supported therein 
by their tips are placed horizontally in a shallow silver bath, and 
immersed just deep enough to allow the projecting convexities to 
dip into the bath. By this artifice these portions are given a 
second coating of silver of any desired thickness. This mode of 
procedure, which is termed " sectional" plating, accomplishes the 
intended purpose nicely and satisfactorily. In some establish- 
ments the silvered forks and spoons are placed between plates of 
gutta-percha of corresponding shape, and held together by rubber 
bands. In these plates the portions to be provided with an extra 
coating of silver are cut out. By suspending the forks and spoons 
thus protected in the bath, the unprotected places receive a further 
layer of silver, the outlines of which are later on smoothed down 
with the burnisher. 

"Stopping off." — Stopping off is the manipulation by which 
certain parts of a metallic article, which may be already covered 
with an electro-deposit on its whole surface, are coated with an- 
other metal. For instance, if it is desired to gild the parts in relief 
of an object the other portions are " stopped off," and vice versa. 
Stopping off varnish is prepared by dissolving asphalt or dammar 
with an addition of mastic in oil of turpentine. Apply with a 
brush, and after thoroughly drying the articles in the drying cham- 
ber place them for one hour in very cold water, whereby the 



DEPOSITION OF SILVER. 219 

varnish hardens completely. After electro-plating the varnish is 
removed, best with benzine, the article plunged in hot water and 
dried in sawdust. 

For a varnish that will resist the solvent power of the hot alka- 
line gilding liquid Gore recommends the following composition : 
Translucent rosin 10 parts, yellow beeswax 6, extra-fine red 
sealing-wax 4, finest polishing rouge 3. 

Silvering by contact, by immersion and cold silvering with paste. 
— For silvering by contact with zinc the bath prepared according 
to formula II. may be used, adding about 77 grains more of 
cyanide of potassium per quart. The articles are to be prepared 
in the same manner as for silvering by weight and quicked in a 
weak quicking solution. Before placing the articles in the bath 
they are wrapped round with bright zinc wire, or are brought in 
contact, while in the bath, with a bright strip of zinc, care being 
had to frequently change the points of contact to prevent the 
formation of stains. As previously mentioned, by the contact of 
the metal to be silvered with the electro-positive zinc, a weak 
current is produced which effects the deposition of the silver, but 
this taking place very slowly it is best to heat the silver bath. 
Silver being at the same time deposited upon the zinc the latter 
must be frequently freed from the deposit and brightened .by 
means of a file or emery paper. 

By contact with zinc, silver may also be deposited in one of the 
following baths for silvering by immersion : Crystallized nitrate of 
silver 5.64 drachms, 98 per cent, potassium cyanide 1.23 ozs., 
water 1 quart. To prepare the bath dissolve the silver salt in 
1 pint of distilled water, then the potassium cyanide in the re- 
maining pint of water and mix the two solutions. The bath is 
heated in a porcelain or enamelled iron vessel to between 176° 
and 194° F., and the thoroughly cleansed and pickled objects 
are immersed in it until uniformly coated ; previous quicking is 
not required. The deposit is lustrous if the articles are left but a 
short time in the bath, but becomes dull when they remain longer ; 
in the first case the deposit is a mere film, and, while it is some- 
what thicker in the latter, it can under no circumstances be called 
solid. 

The bath gradually works less effectively and finally ceases to 



220 



ELECTRO-DEPOSITION OF METALS. 



silver, when it may be attempted to restore its action by the addi- 
tion of 2f to 5 J drachms of potassium cyanide per quart. Should 
this prove ineffectual, the content of silver is nearly exhausted, and 
the bath is evaporated to dryness, and the residue added to the 
silver waste. Frequent refreshing of the bath with silver salt 
cannot be recommended, the silvering always turning out best in 
a fresh bath. 

A solution of nitrate of silver in sodium sulphide is, according 
to Roseleur, very suitable for silvering by immersion. The solu- 
tion is prepared by pouring into a moderately concentrated solu- 
tion of sodium sulphide, with constant stirring, solution of a silver 
salt until the precipitate of silver sulphide formed begins to be 
dissolved with difficulty. This bath can be used cold or warm, 
fresh solution of silver being added when it commences to lose its 
effect. If, however, the bath is not capable of dissolving the 
silver sulphide formed, concentrated solution of sodium sulphide 
has to be added. 

For the preparation of the solution of sodium sulphide, Rose- 
leur recommends the following method : — 

Fig. 85. 




Into a- tall vessel of glass or porcelain (Fig. 85), introduce 5 
quarts of water, and 4 pounds of crystallized soda, after pouring 
in mercury about an inch or so deep, to prevent the glass tube 



DEPOSITION OF SILVER. 221 

through which the sulphurous acid is introduced from being 
stopped up by crystals. The sulphurous acid is evolved by heat- 
ing copper turnings with concentrated sulphuric acid, washing the 
gas in a Woulff bottle filled an inch or so deep with water, and 
introducing it into the bottle containing the soda solution, as 
shown in the illustration. A part of the soda becomes trans- 
formed into sodium sulphide, which dissolves, and a part is pre- 
cipitated as carbonate. The latter, however, is transformed into 
sodium sulphite by the continuous action of sulphurous acid, and 
carbonic acid gas escapes with effervescence. When all has be- 
come dissolved, the passage of sulphurous acid should be continued 
until the liquid slightly reddens blue litmus paper, and then 
allowed to stand aside for 24 hours. At the end of that time a 
certain quantity of crystals will be found upon the mercury, and 
the liquid above, more or less colored, constitutes the sodium sul- 
phide of the silvering bath. The liquid sodium sulphide thus 
prepared should be stirred with a glass rod to eliminate the car- 
bonic acid which may still remain in it. The liquid should then 
be again tested with litmus paper ; and if the blue color is strongly 
reddened, carbonate of soda is cautiously added, little by little, 
in order to neutralize the excess of sulphurous acid. On the 
other hand, if red litmus paper becomes blue, too much alkali is 
present, and more sulphurous acid gas must be passed through 
the liquid, which is in the best condition for our work, when it 
turns litmus paper violet or slightly red. The solution should 
mark from 22° to 26° Be., and should not come in contact with 
iron, zinc, tin, or lead. 

As will be seen, this mode of preparing the sodium sulphide 
solution is somewhat troublesome, and it is, therefore, recom- 
mended to proceed as follows : Prepare a saturated solution of 
commercial sodium sulphide ; the solution will show an alkaline 
reaction, the commercial salt frequently containing some sodium 
carbonate. To this solution add, with stirring, solution of bisul- 
phite of sodium saturated at 122° F., until blue litmus paper is 
slightly reddened. Then add to this solution concentrated solu- 
tion of nitrate of silver until the flakes of silver sulphide sepa- 
rated begin to dissolve with difficulty. 

The immersion-bath, prepared according to one or the other 



222 ELECTRO-DEPOSITION OF METALS. 

method, works well and has the advantage of producing silvering 
of a beautiful lustre, such as is desirable for many cheap articles. 
By allowing the articles to remain for a longer time in the bath, 
the lustrous deposit becomes dull. For the production of a 
lustrous coating the bath should always be used cold. It must 
further be protected, as much as possible, from the light, as other- 
wise gradual decomposition takes place. 

According to Dr. Ebermayer, the composition of a silver bath 
for immersion is as follows : Dissolve 1.12 ounces of nitrate of 
silver in water, and precipitate the solution with caustic potash ; 
then thoroughly wash the precipitated silver oxide, and dissolve 
it in 1 quart of water, which contains 3.52 ounces of potassium 
cyanide in solution ; and finally dilute the w T hole with 1 quart 
more of water. For silvering, the bath is heated to the boiling 
point, and the silver withdrawn may be replaced by the addition 
of moist silver oxide as long as complete dissolution takes place. 
When the silvering is no longer beautiful, and of a pure white 
color, the bath is useless, and is then evaporated. Experiments 
with a bath prepared according to the above directions were not 
satisfactory, the coating being dull and adhering badly. 

The process of coating with a thin film, or rather coloring with 
silver, small articles such as hooks and eyes, pins, etc., differs from 
the above-described immersion process, which effects the silvering 
in a few seconds, in that the articles require to be boiled for a 
longer time. The process is as follows : Prepare a paste from 
14.11 drachms of nitrate of silver, precipitated as chloride of 
silver ; 44 ounces of cream of tartar, and a like quantity of com- 
mon salt, by precipitating the solution of the nitrate of silver 
with hydrochloric acid, washing the chloride of silver and mix- 
ing it with the above-mentioned quantities of cream of tartar 
and common salt, and sufficient water to a paste, which is kept in 
a dark glass vessel to prevent the chloride of silver from being 
decomposed by the light. Small articles of copper or brass are 
first freed from grease, and pickled. Then heat in an enamelled 
kettle 3 to 5 quarts of rain-water to the boiling point ; add 2 or 
3 heaping tablespoonfuls of the above-mentioned paste, and bring 
the metallic objects contained in a stone- ware sieve into the bath 
and stir them diligently with a rod of glass or wood. Before 



DEPOSJTIOK OF SILVER. 223 

placing a fresh lot of articles in the bath additional silver paste 
must be added. If finally the bath acquires a greenish color, 
caused by dissolved copper, it is no longer suitable for the pur- 
pose, and is then evaporated and added to the silver residues. 

Cold silvering with paste. — In this process, an argentiferous paste, 
composed as given below, is rubbed, by means of the thumb, a 
piece of soft leather or rag upon the cleansed and pickled metallic 
surface (copper, brass or other alloys of copper) until it is entirely 
silvered. The paste may also be rubbed in a mortar with some 
water to a uniform thinly-fluid mass, and applied with a brush 
to the surface to be silvered. By allowing the paste to dry natu- 
rally or with the aid of a gentle heat, the silvering appears. The 
application of the paste by means of a brush, is chiefly made use 
of for decorating with silver, articles thinly gilded by immersion. 
For articles not gilded, the above-mentioned rubbing on of the 
stiff paste is to be preferred. 

Composition of argentiferous pastes. — I. Silver in the form of 
freshly precipitated chloride of silver *0.35 oz., common salt 
0.35 oz., potash 0.7 oz., whiting 0.52 oz., and water a sufficient 
quantity to form the ingredients into a stiff paste. 

II. Silver in the form of freshly precipitated chloride of silver 
*0.35 oz., potassium cyanide 1.05 oz., sufficient water to dissolve 
these two ingredients to a clear solution, and enough whiting to 
form the whole into a stiff paste. This paste is also excellent 
for polishing tarnished silver ; it is however poisonous. 

The following composition, which is not poisonous, does excel- 
lent service: Silver in the form of chloride of silver 0.35 oz., 
cream of tartar 0.7 oz., common salt 0.7 oz., and sufficient water 
to form the mixture of the ingredients into a stiff paste. 

Graining. — In gilding parts of watches, gold is seldom directly 
applied upon the copper ; there is generally a preliminary opera- 
tion called graining, by which a grained and slightly dead appear- 
ance is given to the articles. Marks of the file are obliterated by 
rubbing upon a whetstone, and lastly upon an oil-stone. Any 
oil or grease is removed by boiling the parts for a few minutes in 
a solution of 10 parts of caustic soda or potash in 100 of water, 

* From 0.56 oz. of nitrate of silver. 



224 ELECTEO-DEPOSITION OF METALS. 

which should wet them entirely if all the oil has been removed. 
The articles being threaded upon a brass wire, cleanse them rapidly 
in the acid mixture for a bright lustre, and dry them carefully in 
white- wood sawdust. The pieces are fastened upon the even side 
of a block of cork by brass pins with flat heads. The parts are 
then thoroughly rubbed over with a brush entirely free from 
grease, and dipped into a paste of water and very fine pumice- 
stone powder. Move the brush in circles, in order not to rub one 
side more than the other ; thoroughly rinse in cold water, and no 
particle of pumice-stone should remain upon the pieces or the 
cork. Next place the cork and the pieces in a weak mercurial 
solution, composed of water 2J gallons, nitrate or binoxide of 
mercury T ^ oz., sulphuric acid \ oz., which slightly whitens the 
copper. The pieces are passed quickly through the solution and 
then rinsed. This operation gives strength to the graining, which 
without it possesses no adherence. 

The following preparations may be used for graining : I. Silver 
in impalpable powder 2 ozs., finely pulverized cream of tartar 
20 ozs., common salt 4 lbs. II. Silver powder 1 oz., cream of 
tartar 4 to 5 ozs., common salt 13 ozs. III. Silver powder, 
common salt, and cream of tartar, equal parts by weight of each. 
The mixture of the three ingredients must be thorough and effected 
at a moderate and protracted heat. The graining is the coarser 
the more common salt there is in the mixture, and it is the finer 
and more condensed as the proportion of cream of tartar is 
greater, but it is then more difficult to scratch-brush. The 
silver powder is obtained as follows : Dissolve in a glass or por- 
celain vessel f oz. of crystallized nitrate of silver in 2| gallons 
of distilled water, and place 5 or 6 ribbands of cleansed copper, 
f inch wide, in the solution. These ribbands should be long 
enough to allow of a portion of them being above the liquid. 
The whole is kept in a dark place, and from time to time stirred 
with the copper ribbands. This motion is sufficient to loosen the 
deposited silver, and present fresh surfaces to the action of the 
liquor. When no more silver deposits on the copper, the opera- 
tion is complete, and there remains a blue solution of nitrate of 
copper. The silver powder is washed by decantation or upon a 
filter until there remains nothing of the copper solution. 



DEPOSITION OF SILVER. 225 

For the purpose of graining, a thin paste is made of one of the 
above mixtures and water, and spread by means of a spatula upon 
the watch parts held upon the cork. The cork itself is placed 
upon an earthen-ware dish, to which a rotating movement is im- 
parted by the left hand. An oval brush with close bristles, held 
in the right hand, rubs the watch parts in every direction, but 
always with a rotatory motion. A new quantity of paste is added 
two or three times and rubbed in the manner indicated. The 
more the brush and cork are turned the rounder becomes the grain, 
which is a good quality, and the more paste added the larger the 
grain. When the desired grain is obtained the pieces are washed 
and scratch-brushed. The brushes employed are of brass wire, 
as fine as hair, and very stiff and springy. It is necessary to 
anneal them upon an even fire to different degrees ; one soft or 
half-annealed for the first operation or uncovering the grain ; one 
harder for bringing up the lustre ; and one very soft or fully 
annealed, used before gilding for removing any marks which may 
have been made by the preceding tool, and for scratch-brushing 
after gilding which, like the graining, must be done by giving a 
rotatory motion to the tool. If it happens that the same watch 
part is composed of copper and steel, the latter metal requires to 
be preserved against the action of the cleansing acids and of the 
graining mixture by a composition called resist. This consists in 
covering the pinions and other steel parts with a fatty composi- 
tion which is sufficiently hard to resist the tearing action of the 
bristle and wire brushes, and insoluble in the alkalies of the 
gilding bath. A good composition is : Yellow wax 2 parts by 
weight, translucent rosin 3 J, extra fine red sealing-wax 1J, 
polishing rouge 1. Melt the rosin and sealing-wax in a porce- 
lain dish, upon a water bath, and afterwards add the yellow wax. 
When the whole is thoroughly fluid, gradually add the rouge and 
stir with a wooden or glass rod. Withdraw the heat but continue 
the stirring until the mixture becomes solid, otherwise all the 
rouge will fall to the bottom. The flat parts to receive this resist 
are slightly heated and then covered with the mixture, which melts 
and is easily spread. For covering steel pinions employ a small 
gouge of copper or brass fixed to a wooden handle. The metallic 
part of the gouge is heated upon an alcohol lamp, and a small 
15 



226 ELECTRO-DEPOSITION OF METALS. 

quantity of resist is taken with it. The composition soon melts, 
and by turning the tool around, the steel pinion thus becomes 
coated. Use a scratch-brush with long wires, as their flexibility 
prevents the removal of the composition. When the resist is to 
be removed after gilding, put the parts into warm oil or tepid tur- 
pentine, then into a very hot soap water or alkaline solution ; and, 
lastly, into fresh water. Scratch-brush and dry in warm, white 
wood sawdust. The holes of the pinions are cleansed and polished 
with small pieces of very white, soft wood, the friction of which 
is sufficient to restore the primitive lustre. The gilding of parts 
of copper and steel requires the greatest care, as the slightest rust 
destroys their future usefulness. Should some gold deposit upon 
the steel, it should be removed by rubbing with a piece of wood 
and impalpable pumice dust, tin-putty or rouge. 

The gilding of the grained watch parts is effected in a bath 
prepared according to formula I or III, given under " Deposition 
of Gold." 

The silvering of fine copper wire is effected in an apparatus 
similar to that shown on page 170, a reservoir containing potas- 
sium cyanide solution for pickling the cleansed wire being added 
and placed in front of the silver bath. Lustre is imparted to the 
silvered wire by drawing through a draw-plate. Further details 
will be given under " Gilding." 

Incrustations with silver, gold and other metals. — By incrusting 
is understood the inlaying of depressions, produced by engraving 
or etching upon a metallic body, with silver, gold and other metals, 
such as Japanese incrustations, which are made by mechanically 
pressing the silver or gold into the depressions. Such incrusta- 
tions, however, can also be produced by electro-deposition, the 
process being as follows : The design which is to be incrusted 
upon a metal is executed with a pigment of w T hite-lead and glue- 
water or gum-water. The portion not covered by the design is 
then coated with stopping-off varnish. The article is next placed 
in dilute nitric acid, whereby the pigment is first dissolved, and 
next the surface etched, which is allowed to progress to a certain 
depth. Etching being finished, the article is washed in an abund- 
ance of water, and immediately brought into a silver or gold bath, 
in which by the action of the current, the exposed places are filled 



DEPOSITION OF SILVER. 227 

up with metal. This being done the " stopping-off " varnish is 
removed with benzine, the surface ground smooth and polished. 
In this manner one article may be incrusted with several metals, 
for instance, brass may be incrusted with copper, silver and gold ; 
and by oxidizing or coloring portions of the copper, beautiful 
effects can be produced. The principal requisites for these in- 
crustations are manual skill and much patience ; expensive appa- 
ratus is not required, every skilled electro-plater being able to 
execute the work. 

Nielor nielled silvering. — By nielli ng is understood the inlaying 
of designs, produced either by engraving or stamping, with a 
black mixture of metallic sulphides. For preparing the nielling 
composition a certain proportion of sulphur is introduced into a 
stone-ware retort or a deep crucible. A mixture of silver, copper 
and lead is heated in another crucible, and when melted is poured 
into the fused sulphur, which transforms these metals into sul- 
phides. A small portion of sal ammoniac is then added, and, 
after being removed from the crucible, or retort, the product is 
pulverized and is then ready for use. 

The proportions generally used are as follows : — 

Parts. 

Silver 8 2 1 1 

Copper 18 5 6 2 

Lead 13 7 10 4 

Sulphur 96 24 36 5 

The firm of Zachers, of Berlin, claim to have discovered the 
process of making the niel called Tula, after the Russian town of 
the same name. According to them the niel is prepared from 
silver 9 parts, copper 1, lead 1, and bismuth 1. The metals are 
fused and saturated with sulphur. This mixture gives the splendid 
blue which was formerly erroneously considered as steel blue. 

The article to be nielled having been prepared with the graver, 
by etching or stamping, is then covered, hollows and reliefs, with 
the pulverized nielling composition made into a stiff paste with 
solution of sal ammoniac. The article is then heated in the 
muffle until the composition melts when it will be found to 
adhere firmly to the metal. The design is brought out in very 



228 ELECTRO-DEPOSITION OF METALS. 

effective contrast by denuding the portions in relief, without 
touching the hollows which retain a fine black. 

To imitate niel by electro-deposition, the design is executed 
upon the surface with a pigment consisting of white lead and glue 
or gum-water. The portions which are to remain free are coated 
with " stopping off " varnish, and the design is then uncovered by 
etching with very dilute nitric acid. The article is then brought 
as the anode into dilute solution of ammonium sulphide, while a 
small sheet of platinum connected to the negative pole is dipped 
into the solution. Sulphide of silver being formed, the design 
becomes quickly black-gray, and, after removing the " stopping 
off" varnish with benzine, stands out in sharp contrast from the 
white silver. 

Old (antique) silvering. — To give silvered articles an antique 
appearance coat them with a thin paste of 6 parts graphite, 1 red 
ochre and sufficient spirits of turpentine. After drying, a gentle 
rubbing with a soft brush removes the excess of powder, and the 
reliefs are set off (discharged) by means of a rag dipped into alcohol. 

A tone resembling antique silvering is also obtained by brush- 
ing the silvered articles with a soft brush moistened with very 
dilute alcoholic solution of chloride of platinum. 

In order to impart the old silver tinge to small articles, such 
as buttons, rings, etc., they are agitated in the above-mentioned 
paste, and then "tumbled" with a large quantity of dry sawdust 
until the desired shade is obtained. 

Many operators, at the present day, produce the antique silver- 
ing by beginning with the oxidizing process about to be described, 
and setting off the reliefs by means of a hard brush and pumice- 
stone, or Spanish white. This last process is almost exclusively 
used for metallic mountings of books and albums. 

Oxidized silver. — This term is incorrect, as by it is understood 
not an oxidation but a combination with sulphur or chlorine. 
Solution of pentasulphide of potassium (liver of sulphur of the 
shops) is generally used for the purpose. Immerse the articles in 
a solution of 2.75 drachms of liver of sulphur and 5 J drachms 
of ammonium carbonate in 1 quart of water heated to 176° F., 
and allow them to remain until they have acquired the desired 
dark tone. Immediately after immersion the articles become 



DEPOSITION OF SILVER. 229 

pale-gray, then darker, and, finally, deep black-blue. For color- 
ing in this manner the silvering should not be too thin ; for arti- 
cles with a very thick deposit of silver solution of double the 
strength may be used. Very slightly silvered articles cannot be 
oxidized in this manner as the bath would remove the silvering, 
or under the most favorable circumstances produce only a gray 
color. If the operation is not successful, and the articles come 
from the bath stained or otherwise defective, dip them in a warm 
potassium cyanide solution which rapidly dissolves the silver sul- 
phide formed. 

A yellow color is imparted to silvered articles by immersion in 
a hot concentrated solution of chloride of copper, rinsing and 
drying. 

Dissolving silver from silvered articles (stripping). — When a 
silvering operation has failed, or the silver is to be stripped from 
old silvered articles, different methods have to be used according 
to the nature of the basis-metal. Silvered iron articles are 
treated as anode in potassium cyanide solution in water (1 : 20), 
the iron not being brought into solution by potassium cyanide. 
As cathode suspend in the solution a few silver anodes or a copper 
sheet rubbed with an oily rag ; the silver precipitating upon the 
copper sheet but does not adhere to it. Articles, the basis of 
which is copper, are best stripped by immersion in a mixture of 
equal parts of anhydrous (fuming) sulphuric acid and nitric acid 
of 40° Be. This mixture makes the copper passive, it not being 
attacked while the silver is dissolved. Care must, however, be 
had not to introduce any water into the acids, nor let them stand 
without being hermetically closed, since by absorbing water from 
the air they become dilute and may then exert a dissolving effect 
upon the copper. The fuming sulphuric acid may also be heated 
in a shallow pan of enamelled cast-iron to between 300° and 400° 
F. Then at the moment of using it, pinches of dry and pulver- 
ized nitrate of potassium (saltpetre) are thrown into it, and the 
article, held with copper tongs, is plunged into the liquid. The 
silver is rapidly removed, while the copper or its alloys is but 
slightly corroded. According to the rapidity of the solution 
fresh additions of saltpetre are made. All the silver has been 
dissolved when, after rinsing in water and dipping the articles 



230 ELECTRO-DEPOSITION OF METALS. 

into the cleansing acids, they present no brown or black spots, 
that is to say, when they behave like new. In this hot acid 
stripping proceeds more quickly than in the cold acid mixture, 
but the latter acts more uniformly. 

Determination of electro-deposited silvering. — By applying a 
drop of nitric acid of 1.2 specific gravity, in which red chromate 
of potash has been dissolved to saturation, to genuine silvering a 
red stain of chromate of silver is formed. According to Grager 
this method may also be used, to a certain extent, for the recog- 
nition of other white metals which may be mistaken for silver. 
A drop of the mixture applied to German silver becomes brown, 
no red stain appearing after rinsing with water ; upon Britannia 
the drop produces a black stain ; zinc is etched without a colored 
spot remaining behind ; upon amalgamated metals a brownish 
precipitate is formed which does not adhere and is washed away 
by water ; upon tin the drop also acquires a brownish color and 
by diluting with water a yellow precipitate is formed ; upon lead 
a beautiful yellow precipitate is formed. 

Custom-house officers in Germany are directed, by law, to use 
the following process for the determination of genuine silvering : 
Wash a place on the article with ether or alcohol, dry with blot- 
ting paper and apply to the spot thus cleansed a drop of a 1 to 
2 per cent, solution of crystallized bisulphide of soda prepared 
by boiling 1.05 ozs. of sodium sulphite and 2.36 drachms of 
flowers of sulphur with 0.88 oz. of water until the sulphur is dis- 
solved, and diluting to 1 quart of fluid. Allow the drop to re- 
main about ten minutes upon the article and then rinse off with 
water. Upon silver articles a full, round, steel-gray spot is pro- 
duced. Other white metals and alloys, with the exception of 
amalgamated copper, do not show this phenomenon, there appear- 
ing at the utmost a dark ring at the edge of the drop. Amalga- 
mated copper is more quickly colored and acquires a more dead 
black color than silver. 

Recovery of silver from old silver baths, etc. — Old solutions 
which contain silver in the form of a simple salt are easily 
treated. It is sufficient to add to them, in excess, a solution of 
common salt, or hydrochloric acid when all the silver will be pre- 



DEPOSITION OF SILVER. 231 

cipitated in the state of chloride of silver, which, after washing, 
may be employed for the preparation of new baths. 

For the recovery of silver from solutions which contain it as 
cyanide, the solutions may be evaporated to dryness, the residue 
mixed with a small quantity of calcined soda and potassium cyanide, 
and fused in a crucible, whereby metallic silver is formed, which, 
when the heat is sufficiently increased, will be found as a button upon 
the bottom of the crucible; or if it is not desirable to heat to the 
melting point of silver, the fritted mass is dissolved in hot water, 
and the solution containing the soda and cyanide quickly filtered 
off from the metallic silver. The evaporation of large quantities 
of fluid, to be sure, is inconvenient, and requires considerable 
time, but the reducing process above described is without doubt 
the most simple and least injurious. 

According to the wet method the bath is strongly acidulated 
with hydrochloric acid, provision being made for the effectual 
carrying off of the hydrocyanic acid liberated. Remove the pre- 
cipitated chloride of silver and cyanide of copper by filtration, 
and, after thorough washing, transfer it to a porcelain dish and 
treat it with the aid of heat, with hot hydrochloric acid, which 
will dissolve the cyanide of copper. The resulting chloride of 
silver is then reduced to the metallic state by mixing it with four 
times its weight of crystallized carbonate of soda and half its 
weight of pulverized charcoal. The whole is made into a homo- 
geneous paste, which is thoroughly dried, and then introduced 
into a strongly heated crucible. When all the material has been 
introduced the heat is raised to promote complete fusion and to 
facilitate the collection of the separate globules of silver into a 
single button at the bottom of the crucible, where it will be found 
after cooling. If granulated silver is wanted pour the metal in 
a thin stream and from a certain height into a large volume of 
water. 

Still simpler is the reduction of the chloride of silver by pure 
zinc; for this purpose suspend the chloride of silver in water, add 
hydrochloric acid and place pure zinc rods or granulated zinc in 
the fluid. The zinc dissolving, metallic silver is separated which 
is filtered off, washed and dried. 



232 ELECTRO-DEPOSITION OF METALS. 



CHAPTER X. 

DEPOSITION OF GOLD. 

Properties of gold. — Gold is one of the few metals possessing 
a yellow color • precipitated from its solutions with green vitriol 
or oxalic acid, it appears as a brown powder without lustre, which 
on pressing with the burnisher acquires the color and lustre of 
fused gold. Gold is still softer than silver, but possesses con- 
siderable tenacity ; the softness is decreased and the tenacity 
increased by the addition of copper or silver. Gold is the most 
malleable and ductile of the metals ; it may be beaten out into 
leaves not exceeding -ioij-oo-th of a millimetre in thickness. The 
specific gravity of fused gold is 19.35 ; and of precipitated gold 
powder from 19.8 to 20.2. Gold melts at about 2372° F., and 
in fusing exhibits a sea-green color. It preserves its lustre in the 
air, and is not acted upon by any of the ordinary acids. Nitric, 
hydrochloric, or sulphuric acid by itself does not dissolve gold, 
but it dissolves in acid mixtures which develop chlorine, hence, 
in aqua regia, chromic acid, and hydrochloric acid, etc. 

Gold baths. — Electro-gilding may be done with the aid of heat 
or in the cold, large objects being generally gilded in the cold bath, 
and smaller objects in the hot bath. The latter has the advantage 
of requiring less current-strength, besides yielding deposits of 
greater density and uniformity and of sadder, richer tones. Baths 
for hot gilding work with a moderate content of gold — 11 J to 
12 J grains of gold per quart — while baths for cold gilding should 
contain not less than 54 grains per quart. 

Some authors, for instance, Eisner, Briant, Selm, and others, 
give the preference to baths prepared with potassium ferrocyanide, 
while others, like Elkington, and Regnault, work with a solution 
of gold salt and potassium bicarbonate, and Bottcher, Leuchten- 
berg, and others, recommend a solution of cyanide of gold in 
potassium cyanide. With proper treatment of the bath, good 



DEPOSITION OF GOLD. 233 

results may be obtained with either. However, the use of baths 
prepared with potassium ferrocyanide cannot be recommended 
on account of the secondary decompositions which take place 
daring the operation of plating, and because the baths do not 
dissolve the gold anodes. In the following only approved for- 
mulae for the preparation of gold baths will be given : — 

I. Bath for cold gilding. — Fine gold in the form of fulminating 
gold 54 grains, 98 per cent, potassium cyanide 0.35 to 0.5 oz. 
(according to the current-tension used), water 1 quart. 

To prepare this bath dissolve 54 grains of fine gold in aqua 
regia in a porcelain dish heated over a gas or alcohol flame, and 
evaporate the solution to dryness. Continue the heating until 
the solution is thickly fluid and dark-brown, and on cooling con- 
geals to a dark-brown foliated mass. Heating too strongly should 
be avoided as this would cause decomposition and the auric chlo- 
ride would be converted into aurous chloride and eventually into 
metallic gold and escaping chlorine. The neutral chloride of 
gold prepared in this manner is dissolved in 1 pint of water, and 
aqua ammonia added to the solution as long as a yellow-brown 
precipitate is formed, avoiding, however, a considerable excess of 
aqua ammonia. The precipitate of fulminating gold is filtered 
off, washed and dissolved in 1 quart of water containing 0.5 oz. 
of potassium cyanide in solution. The solution is boiled, re- 
placing the w T ater lost by evaporation, until the odor of ammonia 
which is liberated by dissolving the fulminating gold in potassium 
cyanide disappears when it is filtered. Instead of dissolving the 
gold and preparing neutral chloride of gold by evaporating, it is 
more convenient to use 108 grains of chemically pure neutral 
chloride of gold as furnished by chemical works, and precipitate 
the fulminating gold from its solution. 

Too large an excess of potassium cyanide yields gold deposits 
of an ugly pale color. "When working with a more powerful 
current, the excess of potassium cyanide need only be slight; 
with a weaker current, it must be larger. With 10 per cent. 
excess of free potassium cyanide, the most suitable current- 
strength is 3 volts. 

The fulminating gold should not be dried, as in this condition 



234 ELECTRO-DEPOSITION OF METALS. 

it is highly explosive, but should be immediately dissolved while 
in a moist state. 

For cold gilding, Roseleur recommends the following bath : 
II. Fine gold as neutral chloride of gold 0.35 oz., 98 per cent, 
potassium cyanide 0.7 oz., water 1 quart. 

Dissolve the gold salt from 0.35 oz. of fine gold or about 0.7 
oz. of neutral chloride of gold in J pint of water, and the potas- 
sium cyanide in 1 J pints of water, and after mixing the solutions, 
boil for half an hour. The preparation of this bath is more 
simple than that of formula I, but the color of the gold deposit 
obtained with the latter is warmer and sadder than with the 
first. The high content of gold in the bath, prepared according 
to formula II, readily causes a red brown gold deposit, and hence, 
special attention has to be paid to the regulation of the current. 

For those who prefer gold baths prepared with yellow prussiate 
of potash instead of potassium cyanide, the following formula 
for cold gilding is given : — 

III. Yellow prussiate of potash (potassium ferrocyanide) 0.5 
oz., carbonate of soda 0.5 oz., fine gold (as chloride of gold or 
fulminating gold) 30.75 grains, water 1 quart. 

To prepare the bath, heat the solutions of the yellow prussiate 
of potash and of the carbonate of soda in the water to the boiling 
point, add the gold salt, and boil \ hour, or with the use of freshly 
precipitated fulminating gold until the odor of ammonia disap- 
pears. After cooling, the solution is mixed with a quantity of 
distilled water corresponding to the water lost by evaporation, 
and filtered. This bath gives a beautiful bright gilding upon all 
metals, even upon iron and steel. Suitable current-strength 3.25 
to 3.26 volts. 

Gold bath for hot gilding. — IV. Fine gold (as fulminating gold) 
15.4 grains, 98 per cent, potassium cyanide 77 grains, water 1 
quart. 

This bath is prepared in the same manner as that according to 
formula I, from 15.4 grains of fine gold, which is converted into 
neutral chloride of gold by dissolving in aqua regia and evapora- 
ting; or dissolve directly 29.32 to 30.75 grains of chemically 
pure neutral chloride of gold in water, precipitate the gold as 
fulminating gold with aqua ammonia, wash the precipitate, dis- 



DEPOSITION OF GOLD. 235 

solve it in water containing the potassium cyanide, and heat until 
the odor of ammonia disappears, replacing the water lost by evapo- 
ration. This bath yields a beautiful sad gilding of great warmth. 
All that has been said in regard to the content of potassium 
cyanide in the bath prepared according to formula I, also applies 
to this bath. The temperature should be between 158° and 176° 
F., and the current-strength 2.0 to 2.5 volts. 

Roseleur recommends for hot gilding : V. Chemically pure 
crystallized sodium phosphate 2.11 ozs., neutral sodium sulphide 
0.35 oz., potassium cyanide 30.86 grains, fine gold (as chloride) 
15.43 grains, distilled water 1 quart. 

If this bath is to serve for the direct gilding of steel only 15.43 
instead of 30.86 grains of potassium cyanide are to be used. 
Dissolve in a porcelain dish, with the aid of moderate heat, the 
sodium phosphate and sodium sulphide, and when the solution is 
cold, add the neutral chloride of gold prepared from 15.43 grains 
of gold = about 30.86 grains of commercial chloride of gold, and 
the potassium cyanide; for use heat the bath to between 158° 
and 167° F. 

Many electro-platers prepare the gold baths with the assistance 
of the electric current. For this purpose prepare a solution of 
3.52 ozs. of potassium cyanide (98 to 99 per cent.), per quart of 
water, and after heating to between 122° and 140° F., conduct 
the current of two Bunsen elements through two sheets of gold, 
not too small, which are suspended as electrodes in the potassium 
cyanide solution. The action of the current is interrupted when 
the solution is so far saturated with gold that an article immersed 
in it and connected to the negative pole in place of the other gold 
sheet is gilded with a beautiful warm tone. By weighing the 
sheet of gold serving as anode, the amount of gold which has 
passed into the solution is ascertained. According to English 
authorities a good gold bath prepared according to this method 
should contain 3.52 ozs. of potassium cyanide and 0.7 oz. of fine 
gold per quart of water. 

The only advantage of this mode of preparing the baths is that 
it excludes a possible loss of gold which may occur in dissolving 
gold, evaporating the gold solution, etc., by breaking the vessel 
containing the solution. However, by using commercial chemically 



236 ELECTRO-DEPOSITION OF METALS. 

pure chloride of gold such loss is avoided, and the baths prepared 
according to the formulae given yield richer tones than a gold bath 
produced by electrolysis. Besides the preparation of the gold 
bath with the assistance of the electric current can only be con- 
sidered for smaller baths, since the saturation of a larger volume 
of potassium cyanide solution requires considerable time, and the 
potassium cyanide is strongly decomposed by long heating. 

Management of gold baths. — It is advisable to keep the content 
of gold in the baths prepared according to the different formula? 
as constant as possible, which is best effected by the use of fine 
gold anodes. Insoluble platinum anodes are more liked in gild- 
ing than for all other electro- plating processes, partly because 
they are cheaper, and partly because they are recommended in 
most books on the subject. However, a bath which has become 
low in gold does not yield a beautiful gold color, and has to be 
frequently strengthened by the addition of chloride of gold, the 
preparation of which consumes time and causes expense, so that 
the use of gold anodes is the cheapest in the end. The employ- 
ment of anodes of platinum strips or platinum wire may, per- 
haps, be advocated for coloring the deposit, i. e., for the purpose 
of obtaining certain tones of color when gilding in the hot bath. 
By allowing the platinum anode to dip only slightly in the bath 
a pale gilding is obtained, because the current thereby becomes 
weaker ; by immersing the anode deeper the color becomes more 
yellow, and by immersing it entirely the tone becomes more red- 
dish. However, instead of producing these effects of the current- 
strength by the anode, which requires the constant presence of the 
operator, it is better to obtain the colorations by means of the 
resistance board. By placing the handle upon " strong" a reddish 
gold tone is obtained, and by placing it upon " weak" a paler gold 
tone, while the beautiful gold-yellow lies in the middle between 
the two extremes. However, since even with the use of gold 
anodes the content of gold in the bath is not entirely restored, 
the bath has after some time to be strengthened, which is effected 
by a solution of fulminating gold or chloride of gold in potassium 
cyanide, according to the composition of the bath. 

Like in the silvering baths, the excess of potassium cyanide in 
the gold baths is also partially converted into potassium carbon- 



DEPOSITION OF GOLD. 



237 



ate by the action of the air, the heat, etc., and it is, therefore, ad- 
visable from time to time to add a small quantity of potassium 
cyanide. 

Gold baths for cold gilding are kept in vats of stone-ware or 
enamelled iron, or small baths, in glass vats, which, to protect 
them against breaking, are placed in a wooden box. Baths for 
hot gilding require enamelled iron vats in which they can be 
heated by a direct fire, or better, by placing in hot water (water 
bath), or by steam. For small gold baths for hot gilding, a 
porcelain dish resting upon a short-legged iron tripod may be 
used. (Fig. 86.) Beneath the iron tripod is a gas burner sup- 
Fig. 86. 




plied with gas by means of flexible India rubber tubing con- 
nected to an ordinary gas burner. Across the porcelain dish are 
placed two glass rods around which the pole-wires are wrapped. 
In heating larger baths in enamelled vats over a direct fire it may 
happen that on the places most exposed to the heat the enamel 
may blister and peel off; it is, therefore, better to heat the baths 
in a water or steam bath. For this purpose have made a box of 
stout iron or zinc sheet and about f inch wider and longer, 
and about 4 inches deeper than the enamelled vat containing the 
gold bath. To keep the level of the water constant the box is to 
be provided with a water inlet and overflow pipe. In this box 



238 ELECTRO-DEPOSITION OF METALS. 

place the vat so that its edges rest upon those of the box and 
make the joints tight with tow. The water bath is then heated 
over a gas flame or upon a hearth, the water lost by evaporation 
being constantly replaced, so that the enamelled vat is always to 
half its height surrounded by hot water. For heating by steam 
the arrangement is the same, only, a valve for the introduction 
and a pipe for the discharge of steam are substituted for the 
water inlet and overflow pipe. 

Execution of gilding. — Like all other electro-plating operations, 
it is advisable to execute gilding with an external source of cur- 
rent ; that is, to use a battery or other source of current separated 
from the bath, and to couple the apparatuses as previously de- 
scribed and illustrated by Figs. 34 and 35. 

To be sure there are still gilders who gild without a battery or 
separate external source of current and obtain good results, the 
process being, as a rule, employed only in gilding small articles. 
The apparatus used for this purpose consists of a glass vessel 
containing the gold solution compounded with a large excess of 
potassium cyanide and a porous clay cell filled with very dilute 
sulphuric acid or common salt solution, which is placed in the 
glass vessel ; care should be taken to have the fluids in both ves- 
sels at the same level. Immerse in the clay cell an amalgamated 
zinc cylinder or zinc plate, to which a copper wire is soldered. 
Outside the cell this copper wire is bent downward, and the arti- 
cle to be gilded, which dips in the gold solution, is fastened to it. 
In working with this apparatus there is always a loss of gold, 
since the gold solution penetrates through the porous cell, and on 
coming in contact with the zinc is reduced by it, the gold being 
separated as black powder upon the zinc. In cleaning the appa- 
ratus this black slime has to be carefully collected and worked for 
fine gold. 

For the sake of greater solidity only articles of silver and copper 
and its alloys should be directly gilded, while all other metals are 
best first brassed or coppered. Cleaning from grease and pickling 
is done in the same manner as described on page 125. The pre- 
paration of the articles for gilding differs from that for silvering 
only in that the surfaces which later on are to appear with high 
lustre are not artificially roughened with emery, pumice or by 



DEPOSITION OF GOLD. 239 

pickling, because, on the one hand, the gold deposit seldom needs 
to be made extravagantly heavy, and the rough surface formed 
would require more laborious polishing with the burnishers ; and, 
on the other, the gold deposits adhere quite well to highly-polished 
surfaces provided the current-strength is correctly regulated, and 
the bath accurately composed according to one of the formula? 
given. Quicking the articles before gilding, which is recom- 
mended by some authors, is not necessary. 

The current-strength must, under no circumstances, be so great 
that a decomposition of water and consequent evolution of hydro- 
gen on the objects takes place, since otherwise the gold would not 
deposit in a reguline and coherent form, but as a brown powder. 
By regulating the current-strength so that it just suffices for the 
decomposition of the bath, and avoiding a considerable surplus, a 
very dense and uniform deposit is formed ; and by allowing the 
object to remain long enough in the bath, a beautiful, dull gold 
deposit can be obtained in all the baths prepared according to the 
formulae given. It may, however, be mentioned, that this mode 
of dull gilding is the most expensive, since it requires a very 
heavy deposit, and it will, therefore, be better to deaden the sur- 
face previous to gilding according to a process to be described 
later on. 

For gilding with cold baths two freshly filled Bunsen elements 
coupled for tension suffice in almost all cases, while for hot baths 
one element is, as a rule, sufficient, if the anode surface is not too 
small. The more electro-positive the metal to be gilded is, the 
weaker the current can and must be. 

Though gold solutions are good conductors and, therefore, the 
portions which do not hang directly opposite the anodes gild well, 
for the solid gilding of larger objects it is recommended to fre- 
quently change their positions except when they are entirely sur- 
rounded by anodes. 

The inner surfaces of hollow-ware, such as drinking cups, milk 
pitchers, etc., are best gilded after freeing them from grease and 
pickling, by filling the vessel with the gold bath and suspending 
a current carrying gold anode in the centre of the vessel, while 
the outer surface of the latter is brought in contact with the 
negative conducting wire. The lips of vessels are gilded by 



240 ELECTRO-DEPOSITION OF METALS. 

placing upon them a cloth rag saturated with the gold bath and 
covering the rag with the gold anode. 

For gilding in the cold bath the process is as follows : The 
objects thoroughly freed from grease and pickled (and if of iron, 
zinc, tin, Britannia, etc., previously coppered), are hung in the 
bath by copper wires where they remain with a weak current 
until in about 8 or 10 minutes they appear uniformly gilded. 
At this stage they are taken from the bath, rinsed in a pot filled 
with water, which after working for some time is added to the 
bath to replace the water lost by evaporation, and brushed with 
a fine brass scratch-brush and tartar solution. They are then 
thoroughly rinsed, again freed from grease by brushing with lime 
paste, and then returned to the bath where they remain until they 
have acquired a deposit of sufficient thickness. 

If it is intended to give them a very heavy deposit, it is advis- 
able to several times scratch-brush them with the use of tartar or 
its solution. For gilding by weight the same plan as given for 
silvering (p. 211) is pursued. 

For gilding with the hot bath the operations are the same with 
the exception that a weaker current is introduced into the bath 
and the time of the gilding process shortened. Frequent scratch- 
brushing also increases the solidity of the deposit and prevents 
the premature turning to a dead brown-black. Since in hot 
gilding more gold than intended is readily deposited, it is especially 
advisable to place a resistance board in the circuit, as otherwise 
the operator must remain standing on the bath and regulate the 
effect of the current by immersing the anodes more or less. 

With a somewhat considerable excess of potassium cyanide, and 
if the objects to be gilded are not rapidily brought in contact with 
the current carrying object rod, hot gold baths cause the solution 
of some metal. Therefore, when silver or silvered objects are 
constantly gilded in them, they yield a somewhat greenish gilding 
in consequence of the absorption of silver, or a reddish gilding due 
to the absorption of copper, if copper or coppered articles are 
constantly gilded in them. Hence, for the production of such 
green or reddish color, gilding baths which have thus become 
argentiferous or cupriferous may be advantageously used. In 
order to obtain a deposit of green or red gold with fresh baths, 



DEPOSITION OF GOLD. 241 

the tone-giving addition of metal must be artificially effected as 
will immediately be seen. 

If, however, such extreme tones are not desired, the content of 
gold in the baths may be exhausted for preliminary gilding with 
the use of platinum anodes, the sad gold color being then given 
in a freshly prepared bath. 

The gold deposits are polished, in the same manner as silver 
deposits, with the burnisher and red ochre, and moistening with 
solution of soap, decoction of flaxseed, or soap root, etc. 

Red gilding. — In order to obtain a red gold with the formulae 
given, a certain addition of cyanide of copper dissolved in potas- 
sium cyanide has to be made to them. The quantity of such 
addition cannot be well expressed by figures since the current- 
strength with which the articles are gilded exerts considerable 
influence. It is best to triturate the cyanide of copper in a 
mortar to a paste with water, and add of this paste to a moder- 
ately concentrated potassium cyanide solution as long as cyanide 
of copper is dissolved. Of this copper solution add, gradually 
and in not too large portions, to the gold solution until, with the 
current-strength used, the gold-deposit shows the desired red tone. 
The absorption of copper by the bath may also be effected by 
replacing the gold anodes by copper anodes and circulating the 
current (suspending a few gold anodes to the object rod). The 
direct addition of cyanide of copper is, however, preferable. 

For the determination of the content of copper required for 
the purpose of obtaining a beautiful red gold, a bath for hot 
gilding which contained 10.8 grains of gold per quart was com- 
pounded with a solution of cyanide of copper in potassium cyanide 
with 1.08 grains content of copper. The tone of the gilding, 
which previously was pure yellow, immediately passed into a pale 
red gold. By the further addition of 1.08 grains of copper a 
fiery red gold tone was obtained, while a third addition of 1.08 
grains of copper yielded a color more approaching that of copper 
than of gold. These experiments show that 20 per cent, of cop- 
per of the weight of gold contained in the bath seems to be the 
most suitable proportion for obtaining a beautiful red gold. 

Green gilding. — To obtain a greenish gilding, solution of 
cyanide or chloride of silver in potassium cyanide has to be 
16 



242 ELECTKO-DEPOSITION OF METALS. 

added to the gold bath. It is not easy to prepare greenish gild- 
ing of a pleasing color, and to obtain it, the current-strength must 
be accurately proportioned to the object-surface, siuce with too 
weak a current silver predominates in the deposit, the gilding 
then turning out whitish, while too strong a current deposits too 
much gold in proportion to silver, the gilding becoming yellow, 
but not green. 

Rose-color gilding may be obtained by the addition of suitable 
quantities of copper and silver solution, but such coloration, like 
those previously mentioned, requires much attention and reflec- 
tion. Hot gold baths are most suitable for such colorations. 

For the sake of completeness, a method of gilding, which is 
a combination of fire-gilding with electro-deposition, may be 
mentioned. 

According to du Fresne, the articles are plated, with the assist- 
ance of the current, in a mercury solution of cyanide of mercury 
in potassium cyanide with additions of carbonate and phosphate 
of soda, then gilded in an ordinary gilding bath, next again coated 
with mercury, then again gilded, and so on, until a deposit of 
sufficient thickness is obtained. The mercury is then evaporated 
over glowing coals, the articles scratch-brushed and polished. 

According to another process, the articles are gilded with a 
strong current in a bath consisting of 98 per cent, potassium 
cyanide 1.2 ozs., cyanide of gold 92 J grains, cyanide of mercury 
92J grains, distilled water 1 quart. The articles being sufficiently 
gilded, the mercury is evaporated, and the articles, after scratch- 
brushing, are burnished. 

Dead gilding. — As previously mentioned, a beautiful dead gold- 
deposit may be obtained by the use of any of the formulae given and 
a correctly regulated current, and allowing sufficient length of time 
for gilding ; but the heavy deposit of gold required for this pro- 
cess makes it too expensive, and it is therefore advisable to pro- 
duce dead gilding without excessively heavy deposits by previous 
deadening of the basis-surface. The process of graining has 
already been described on p. 223 ; another method is to deaden 
the first thin deposit of gold with the deadening scratch-brush, 
and then to give a second deposit of gold, which also turns out dead 
upon the deadened surface. However, this operation of deadening 



DEPOSITION OF GOLD. 243 

with the scratch-brush requires considerable skill, and it is there- 
fore best to deaden the surface according to one of the following 
methods : — 

For this purpose, the mixture of 1 volume of saturated solution 
of bichromate of potash, and 2 volumes -of concentrated hydro- 
chloric acid, mentioned on p. 124, may be used. Brass articles 
are allowed to remain in the mixture several hours, and are then 
quickly drawn through the bright-dipping bath ; 

Or, by depositing upon the articles a coating of frosted silver 
and then gilding in a good gold bath. Unfortunately, this method 
is somewhat expensive, and the burnished parts are greenish. 
Moreover, the intermediary coat of silver is easily affected by 
sulphurous gases, the gilding being thereby blackened. 

More advantageous is the process of providing the articles with 
a dead-copper coating in the acid galvanoplastic copper bath, 
then quicking them, and finally gilding. This gilding is very 
handsome in lustre and color. 

Zinc objects are first heavily coppered in a cyanide of copper 
bath, and are then deadened in the acid copper bath (see " Galvano- 
plasty"), care being had that the suspending wires are in contact 
with the object-rod before immersing the coppered zinc object 
in the bath. However, this process of coppering zinc in the 
acid copper bath is a very delicate operation, it being frequently 
seen that even with an apparently very heavy coppering in the 
cyanide of copper bath, brownish-black spots appear on the 
objects when brought into the acid bath, the copper being de- 
posited on these spots in a pulverulent form by the contact of the 
acid bath with the zinc. If this is observed, the objects have to 
be immediately taken from the bath, and after thorough scratch- 
brushing, again thoroughly and quickly coppered in the cyanide 
of copper bath before returning them to the acid copper bath. It 
may be recommended first to provide the previously coppered ob- 
jects with a thin coat of nickel, and then to copper them in the 
acid copper bath. 

Coloring of the gilding. — It has been frequently mentioned that 
the most rational and simple process of giving certain tones of 
color to the gilding, is by means of a stronger or weaker current. 
Many operators however cling to the old method of effecting the 



244 ELECTRO-DEPOSITION OF METALS. 

coloration by gilder's wax or brushing with certain mixtures, and 
for this reason, this process, which is generally used for coloring 
fire-gilding, shall be briefly mentioned. 

To impart to the gold-deposit a redder color, the gilding wax 
is prepared with a greater content of copper, while for greenish 
gilding, more zinc salt is added. There are innumerable receipts 
for the preparation of gilding wax, nearly every gilder having 
his own receipt, which he considers superior to all others. Only 
two formulae which yield good results will here be given, one (I) 
for reddish gilding and one (II) for greenish gilding. 

I. Wax, 12 parts by weight, pulverized verdigris 8, pulverized 
sulphate of zinc 4, copper scales 4, borax 1, pulverized blood- 
stone 6, copperas 2. 

II. Wax, 12 parts by weight, pulverized verdigris 4, pul- 
verized sulphate of zinc 8, copper scales 2, borax 1, pulverized 
bloodstone 6, copperas 2. 

Gilder's wax is prepared as follows : Melt the wax in an iron 
kettle, add to the melted mass, with constant stirring, the other 
ingredients, pulverized and intimately mixed, in small portions 
and stir until cold, so that the powder cannot settle on the bottom 
or form lumps. Finally mould the soft mass into sticks about J 
inch in diameter. 

The operation for applying the gilder's wax is as follows : Coat 
the heated gilded articles uniformly with the wax and burn oif 
over a charcoal fire, frequently turning the articles. After the 
extinguishment of the wax flames plunge the articles into water, 
scratch -brush with wine vinegar, dry in sawdust, and polish. 

To give gilded articles a beautiful rich appearance the follow- 
ing process may also be used : Mix 3 parts by weight of pulver- 
ized alum, 6 of saltpetre, 3 of sulphate of zinc, and 3 of com- 
mon salt, with sufficient water to form a thinly-fluid paste. 
Apply this paste as uniformly as possible to the articles by means 
of a brush, and after drying, heat the coating upon an iron plate 
until it turns black, then wash in water, scratch-brush with wine- 
vinegar, dry and polish. 

According to a French receipt the same result is attained by 
mixing, pulverized blue vitriol 3 parts by weight, verdigris 7, 
sal ammoniac 6, and saltpetre 6, with acetic acid 31 ; immersing 



DEPOSITION OF GOLD. 245 

the gilded articles in the mixture or applying the latter with a 
brush, then heating the objects upon a hot iron plate until they 
turn black, and after cooling, pickling in concentrated sulphuric 
acid. 

Some gilders improve bad tones of gilding by immersing the 
articles in dilute solution of nitrate of mercury until the gilding 
appears white ; the mercury is then evaporated over a flame and 
the articles are scratch-brushed. Others apply a paste of pulver- 
ized borax and water, heat until the borax melts, and then quickly 
immerse in dilute sulphuric acid. 

Incrustations with gold, are produced in the same manner as in- 
crustations with silver described on p. 226. 

Gilding of metallic wire and gauze. — Fine wire of gilded copper 
and brass is much used in the manufacture of metallic fringes and 
lace, for epaulettes and other purposes. The fine copper and brass 
wires being drawn through the draw-irons and wound upon spools 
by special machines, and hence not touched by the hands, freeing 
from grease may, as a rule, be omitted. The first requisite for 
gilding is a good winding machine, which draws the wires through 
the gold bath and wash boxes, and further effects the winding of 
the wire upon spools. The principal demand made in the con- 
struction of such a machine is, that by means of a simple manipu- 
lation a great variation in the speed with which the wire or gauze 
passes through the gold bath can be obtained. This is necessary 
in order to be able to regulate the thickness of the gilding by the 
quicker or slower passage of the wire. A machine well adapted 
for this purpose is that constructed by J. W. Spaeth and shown 
in Fig. 87. 

The variation in the passage of the wire is attained by the 
two friction pulleys F, which sit upon a common shaft with the 
driving pulley JR, and transmit their velocity by means of the 
friction-pistons KK' to the friction-pulley F' f which is firmly con- 
nected to the belt-pulley R driving the spool spindle. Since by 
a simple device the pistons iTand K' may be shifted, it is clear that 
the transmission of the number of revolutions from F to F' is de- 
pendent on the position of the friction pistons isT and K f , and that 
the velocity will be the greater the shorter the distance they are 
from the centre of the friction-pulleys F and F' . In order that 



246 



ELECTRO-DEPOSITION OF METALS. 



the friction between F, K, and F' may always be sufficient for the 
transmission of the motion, even when the pistons are worn, four 
weights, G, are provided, which press the above-mentioned parts 
firmly against each other. 




In front of each spool of this machine is inserted a small 
enamelled iron vat which contains the gold bath, and is heated by 
a gas flame to about 167° F. Between this bath and the winding 
machine is another small vat with hot water in which the gilded 
wire is rinsed. 

The wires unwind from a reel placed in front of the gold baths, 
run over a brass drum which is connected to the negative pole of 



Fig. 





the source of current, and transmits the current to the wires ; the 
dipping of the wires into the gold bath is effected by porcelain 
drums, which are secured to heavy pieces of lead placed across the 



DEPOSITION OF GOLD. 247 

vats as shown in Fig. 88. The gilded wire being wound upon 
the spools of the winding machine, these spools are removed and 
thoroughly dried in the drying chamber. The wire is then again 
reeled off on to a simple reel, in doing which it is best to pass it 
through between two soft pieces of leather to increase its lustre. 

The most suitable gold bath is that prepared according to 
formula IY ; the current-strength should be from 6 to 8 volts, 
which will produce a deposit of sufficient thickness even with the 
wire passing at the most rapid rate through the bath. 

Gilding by contact, by immersion, and by friction. — For contact 
gilding by touching with zinc, formula? I, II, IV, and V may be 
used, IV and V being especially suitable if the addition of potas- 
sium cyanide is somewhat increased, and the baths are sufficiently 
heated. 

A contact gold bath prepared with yellow prussiate of potash 
according to the following formula also yields a good deposit : 
VI. Fine gold as chloride of gold 54 grains, yellow prussiate of 
potash 1 oz., potash 1 oz., common salt 1 oz., water 1 quart. The 
bath is prepared as given for formula III ; for use, heat it to boiling. 

Gilding by contact is done the same way as silvering by con- 
tact. The points of contact must be frequently changed, since in 
the gold bath intense stains are still more readily formed than in 
the silver bath. 

For baths for gilding by dipping the following two formulae have 
stood the test : I. Crystallized sodium pyrophosphate 2.82 ozs., 
12 per cent, prussic acid 4.51 drachms, crystallized chloride of 
gold 1.12 drachms, water 1 quart. Heat the bath to the boil- 
ing point, and immerse the pickled objects of copper or its alloys, 
moving them constantly until gilded. Iron, steel, tin and zinc 
should previously be coppered ; coating the objects with mercury 
(quicking) before immersion being entirely superfluous. 

All gold baths prepared with sodium pyrophosphate give rapid 
and beautiful results when fresh, but they have the disadvantage 
of quickly decomposing, and consequently can seldom be com- 
pletely exhausted. In this respect the following formula answers 
much better : — 

II. Crystallized sodium phosphate 2.82 drachms, chemically 
pure .caustic potash 1.69 drachms, chloride of gold 0.56 drachm, 



248 ELECTRO-DEPOSITION OF METALS. 

98 per cent, potassium cyanide 9.03 drachms, water 1 quart. Dis- 
solve the sodium phosphate and caustic potash in j of the water, 
and the potassium cyanide and chloride of gold in the remaining J. 
Heat the solution to the boiling point. The bath can be almost 
entirely exhausted, it not being decomposed by keeping. Should 
the bath become weak, add about 2.82 drachms of potassium 
cyanide, and use it for preliminary dipping until no more gold is 
reduced. To complete the coating the objects subjected to such 
preliminary dipping are then immersed for a few seconds in a 
freshly prepared bath of the composition given above. 

The layer of gold formed is in all cases very thin, the amount 
of gold deposited corresponding to the quantity of basis-metal 
which has been dissolved. 

Gilding by friction. — This process is variously termed gilding 
with the rag, with the thumb, with the cork. It is chiefly employed 
upon silver, though sometimes also upon brass and copper. The 
operation is as follows : Dissolve 1.12 to 1.69 drachms of chloride 
of gold in as little water as possible, to which has previously been 
added 0.56 drachm of saltpetre. Dip in this solution small linen 
rags, and, after allowing them to drain off, dry them in a dark 
place. These rags saturated with gold solution are then charred 
to tinder at not too great a heat, whereby the chloride of gold is 
reduced, partially to protochloride and partially to finely divided 
metallic gold. This tinder is then rubbed in a porcelain mortar 
to a fine uniform powder. 

To gild with this powder, dip into it a charred cork moistened 
with vinegar or saltwater and rub, with not too gentle a pressure, 
the surface of the article to be gilded, which must be previously 
cleansed from adhering grease. The thumb of the hand may be 
used in place of the cork, but in both cases care must be had not 
to moisten them too much, as otherwise the powder takes badly. 
After gilding the surface may be carefully burnished. 

For gilding by friction a solution of chloride of gold in an 
excess of potassium cyanide may also be used, after thickening 
the solution to a paste by rubbing in whiting. The paste is ap- 
plied to the previously zincked metals by means of a cork, piece 
of leather, or a brush. Martin and Peyraud, the originators of 
this method, describe the operation as follows : Articles of other 



DEPOSITION OF GOLD. 249 

metals than zinc are placed in a bath consisting of concentrated 
solution of sal ammoniac, in which has been placed a quantity of 
granulated zinc. The articles are allowed to boil a few minutes, 
whereby they acquire a coating of zinc. For the preparation of 
the gilding composition, dissolve 11.28 drachms of chloride of gold 
in a like quantity of water, and add a solution of 2.11 ozs. of 
potassium cyanide in as little water as possible (about 2.8 ozs.). 
Of this solution add so much to a mixture of 3.52 ozs. of fine 
whiting and 2.82 drachms of pulverized tartar that a paste is 
formed which can be readily applied with a brush to the article 
to be gilded. When the article is coated, heat it to between 140° 
and 158° F. After removing the dry paste by washing the 
gilding appears and can be polished with the burnisher. 

Removing gold from gilded articles — "Stripping" — Gilded 
articles of iron and steel are best stripped by treating them as the 
anode in a solution of from 2 to 2| ozs. of 98 per cent, potas- 
sium cyanide in 1 quart of water, and suspending a copper plate 
greased with oil or tallow as the cathode. Gilded silverware is 
readily stripped by heating to glowing and then immersing in 
dilute sulphuric acid, whereby the layer of gold cracks off, the 
glowing and immersing in dilute sulphuric acid being repeated 
until all the gold is removed. Before glowing and immersing in 
dilute sulphuric acid, the articles may first be provided with a 
coating of a paste of sal ammoniac, flowers of sulphur, borax, 
and nitrate of potash, which is allowed to dry. On the bottom 
of the vessel containing the dilute sulphuric acid the gold will be 
found in laminae and scales, which are boiled with pure sulphuric 
acid, washed, and finally dissolved in aqua regia, and made into 
chloride of gold or fulminating gold. 

To strip articles of silver, copper, or German silver which will 
not bear glowing, the solution of gold may be effected in a mix- 
ture of 1 lb. of fuming sulphuric acid, 2.64 ozs. of concentrated 
hydrochloric acid, and 1.3 ozs. of nitric acid of 40° Be. Dip 
the articles in the warm acid mixture and observe the progressive 
action of the mixture by frequently removing the articles from 
it. The articles to be treated must be perfectly dry before 
immersing in the acid mixture, and care must be had to preserve 



250 ELECTRO-DEPOSITION OF METALS. 

the latter from dilution with water in order to prevent the acids 
from acting upon the basis-metal. 

Determination of genuine gilding. — Objects apparently gilded 
are rubbed upon the touchstone and the streak obtained is treated 
with pure nitric acid of 1.30 to 1.35 specific gravity. The metal 
contained in the streak thereby dissolves, and as far as it is not 
gold disappears, while the gold remains behind. The stone 
should be thoroughly cleansed before each operation, and the 
streak should be made not with an edge or a corner of the object 
to be tested, but with a broader surface. If no gold remains 
upon the stone, but there is, nevertheless, a suspicion of the 
article being slightly gilded, proceed with small articles as fol- 
lows : Take hold of the article with a pair of tweezers, and 
after washing it first with alcohol, and then with ether, and 
drying upon blotting paper, pour over it in a test glass, cleansed 
with alcohol or ether, according to the weight of the article 0.084 
to 5.64 drachms of nitric acid of 1.30 specific gravity free from 
chlorine. The article will be immediately dissolved, and if it has 
been gilded never so slightly, perceptible gold spangles will remain 
upon the bottom of the glass. 

{Recovery of gold from gold baths, etc. — To recover the gold 
from old cyanide gilding baths, evaporate the bath to dryness, 
mix the residue with litharge and fuse the mixture. The gold is 
contained in the lead button thus obtained. The latter is then 
dissolved in nitric acid, whereby the gold remains behind in the 
form of spangles. These spangles are filtered off and dissolved 
in aqua regia. 

The following method is used for the recovery of gold by the 
wet process: The bath containing gold, silver, and copper, is 
acidulated with hydrochloric acid, which causes a disengagement 
of hydrocyanic acid. This gas is extremely poisonous, for which 
reason the operation should be carried on in the open air or where 
there is a good draught or ventilation to carry off the fumes. 
A precipitate consisting of the cyanides of gold and copper, and 
chloride of silver is formed. This is well washed and boiled in 
aqua regia, which dissolves the gold and copper as chlorides, 
leaving the chloride of silver behind. The solution containing 
the gold and copper is evaporated nearly to dryness in order to 



DEPOSITION OF PLATINUM AND PALLADIUM. 251 

remove the excess of acid, the residue is dissolved in a small 
quantity of water and the gold precipitated therefrom as a brown 
metallic powder by the addition of sulphate of iron (copperas). 
The copper remains in solution. 

From the add mixtures serving for dead pickling gold or for 
stripping, the gold is precipitated by solution of sulphate of iron 
(copperas) added in excess. The gold present is precipitated as a 
brown powder mixed with ferric oxide. This powder is filtered off, 
and treated in a porcelain dish with hot hydrochloric acid which 
dissolves the iron. The gold which remains behind is then fil- 
tered off, and after washing dissolved in aqua regia in order to 
work the solution into fulminating gold or neutral chloride of 
gold. 



CHAPTEE XI. 

DEPOSITION OF PLATINUM AND PALLADIUM. 

1. Deposition of Platinum. 

Properties of platinum. — Pure platinum is white with a grayish 
tinge ; it is as soft as copper, malleable, and very ductile. At a 
white heat it can be welded, but is fusible only with the oxyhy- 
drogen blow-pipe or by the electric current. Its specific gravity 
is 21.4. 

Air has no oxidizing action upon platinum ; it is scarcely acted 
upon by any single acid ; prolonged boiling with concentrated sul- 
phuric acid appears to dissolve the metal slowly. The best sol- 
vent for it is aqua regia, which forms the tetrachloride PtCl 4 . 
Chlorine, bromine, sulphur, and phosphorus combine directly 
with platinum, and fusing saltpetre and caustic alkali attack it. 

Besides in the malleable and fused state, platinum may be 
obtained as a very finely divided powder, the so-called platinum 
black, which is precipitated with zinc from dilute solution of 
platinum chloride acidulated with hydrochloric acid. 

Platinum baths. — The platinum baths formerly proposed did 
not yield quite satisfactory results, the content of platinum being 



252 ELECTRO-DEPOSITION OF METALS. 

too small in some of them, while with others, dense deposits could 
not be obtained. A new formula by Bottger gives however quite 
a good bath : A moderately dilute solution of sodium citrate is 
added to platoso-ammonium chloride, until an excess of the latter 
no longer dissolves, even after continued boiling. The follow- 
ing proportions have been found very suitable : Dissolve 17 J 
ozs. of citric acid in 2 quarts of water, and neutralize with caustic 
soda. To the boiling solution add, with constant stirring, the 
platoso-ammonium chloride freshly precipitated from 2.64 ozs. 
of chloride of platinum, heat until solution is complete, allow 
to cool, and dilute with water to 5 quarts. To decrease the re- 
sistance of the bath, 0.7 or 0.8 oz. of sal ammoniac may be added ; 
a larger addition, however, causing the separation of dark-colored 
platinum. 

The platoso-ammonium chloride is prepared by adding to a con- 
centrated solution of chloride of platinum concentrated solution 
of sal ammoniac until a yellow precipitate is no longer formed on 
adding a further drop of sal ammoniac. The precipitate is filtered 
off and brought into the boiling solution of sodium citrate. This 
bath works very uniformly if the content of platinum is from 
time to time replenished. 

" The Bright Platinum Plating Company," of London, has 
recently patented the following composition of a platinum bath : 
Chloride of platinum 0.98 oz., sodium phosphate 19f ozs., ammo- 
nium phosphate 3.95 ozs., sodium chloride 0.98 oz., and borax 
0.35 oz., are dissolved, with the aid of heat, in 6 to 8 quarts of 
water, and the solution is boiled for 10 hours, the water lost by 
evaporation being constantly replaced. The results obtained with 
this bath were not much better than with Bottger's. 

Dr. W. H. Wahl gives the following directions for preparing 
platinum baths :* — 

Alkaline platinate bath. — Platinic hydrate 2 ozs., caustic potassa 
(or soda) 8 ozs., distilled water 1 gallon. 

Dissolve one-half of the caustic potassa in a quart of distilled 
water, add to this the platinic hydrate in small quantity at a time, 
facilitating solution by stirring with a glass rod. When solution 

* Journal of the Franklin Institute, July, 1890. 



DEPOSITION OF PLATINUM AND PALLADIUM. 253 

is effected, stir in the other half of alkali dissolved in a quart of 
water ; then dilute with enough distilled water to form one gallon 
of solution. To hasten solution, the caustic alkali may be gently 
heated, but this is not necessary, as the platinic hydrate dissolves 
very freely. This solution should be worked with a current of 
about two volts, and will yield metal of an almost silvery white- 
ness upon polished surfaces of copper and brass, and quite freely. 
There should be slight, if any, perceptible evolution of hydrogen 
at the cathode, but a liberal evolution of oxygen at the anode. 
An addition of a small proportion of acetic acid to this bath 
improves its operation where a heavy deposit is desired. The 
anode must be of platinum or carbon, and owing to the readiness 
with which the metal is deposited, an excess of anode-surface is 
to be avoided. Articles of steel, nickel, tin, zinc or German sil- 
ver will be coated with black and more or less non-adherent plati- 
num ; but by giving objects of these metals a preliminary thin 
electro-deposit of copper in the hot cyanide bath, they may be 
electro-platinized in the alkaline platinate bath equally as well as 
copper. The bath may be worked hot or cold, but it is recom- 
mended to work it at a temperature not exceeding 100° F. It 
may be diluted to one-half the strength indicated in the formula, 
and still yield excellent results. The surface of the objects should 
be highly polished by buffing or otherwise prior to their intro- 
duction into the bath, if the resulting deposit is designed to be 
brilliant. 

The deposition of platinum takes place promptly. In five 
minutes a sufficiently heavy coating will be obtained for most 
purposes. The deposited metal is so soft however that it requires 
to be buffed very lightly. A heavier deposit will appear gray in 
color, but will accept the characteristic lustre of platinum beneath 
the burnisher. 

An oxalate solution is prepared by dissolving 1 oz. of platinic 
hydrate in 4 ozs. of oxalic acid, and diluting the solution to the 
volume of one gallon with distilled water. The solution should 
be kept acidified by the occasional addition of some oxalic acid. 
The simplest plan of using this bath, and which requires no atten- 
tion to proportions, is simply to work with a saturated solution 
of the oxalate, keeping an undissolved excess always present at 



254 ELECTRO-DEPOSITION OF METALS. 

the bottom of the vessel. An addition of a small quantity of oxalic 
acid now and then will be found advantageous. The double 
salts of oxalic acid with platinum and the alkalies may be formed 
by saturating the binoxalate of the desired alkali with platinic 
hydrate, and maintaining the bath in normal metallic strength by 
the presence of an undissolved residuum of platinous oxalate. 

The double oxalates are not so soluble in water as the simple 
salt. The oxalate baths, both of single and double salts, may be 
worked cold or hot (though not to exceed 150° F.) with a current 
of comparatively low pressure. The metal will deposit bright, 
reguline and adherent on copper and brass. Other metallic ob- 
jects must receive a preliminary coppering as above. The de- 
posited metal is dense, with a steely appearance, and can be 
obtained of any desired thickness. 

The deposit obtained in the oxalate bath is sensibly harder 
than that from the alkaline platinate bath, and will bear buffing 
tolerably well. 

The phosphate bath may be prepared by the following formula : 

Phosphoric acid, syrupy (specific gravity 1.7), 8 ozs., platinic 
hydrate 1 to 1J ozs., distilled water 1 gallon. 

The acid should be moderately diluted with distilled water, and 
the solution of the hydrate effected at the boiling temperature. 
Water should be added cautiously from time to time to supply 
that lost by evaporation. When solution has taken place, the 
same should be diluted with sufficient water to make the volume 1 
gallon. The solution may be worked cold or heated to 100° F., and 
with a current much stronger than that required for the platinates 
and oxalates. The ammonio (and sodio) platinic phosphates may 
be formed from the simple phosphate by carefully neutralizing 
the solution of the phosphate with ammonia (or soda) ; then ad- 
ding an excess of phosphoric acid, or enough to dissolve the pre- 
cipitate formed, and an additional quantity to insure a moderate 
amount of free phosphoric acid in the bath. The phosphate 
baths will be maintained of normal strength by additions of pla- 
tinic hydrate, the solutions of which will need to be assisted by 
heating the bath, preferably at the close of each day's work. The 
metal yielded by the electrolysis of these phosphate solutions is 
brilliant and adherent. It has the same steely appearance as 



DEPOSITION OF PLATINUM AND PALLADIUM. 255 

that exhibited by the oxalate solutions, but to a less pronounced 
degree. The physical properties of the deposited metal are in 
other respects like those described in connection with that ob- 
tained from the oxalate baths. 

Management of platinum baths. — Copper and brass may be 
directly coated with platinum, but iron, steel and other metals 
have to be previously coppered ; without preliminary coppering 
these metals would soon decompose the platinum bath, indepen- 
dent of the fact that no perfect deposit of platinum can be pro- 
duced upon them without the cementing intermediary layer of 
copper. 

Platinum baths must be used hot and, even then, require a cur- 
rent of 5 to 6 volts. An abundant evolution of gas must appear 
on the objects and the anodes ; the anode-surface (platinum an- 
odes) must not be too small and should be only at a few centimetres 
distance from the objects. Since the platinum anodes do not 
dissolve, the content of platinum in the bath becomes constantly 
smaller, and the bath must from time to time be strengthened. 
It is then heated in a porcelain dish or enamelled vessel to the 
boiling point, some fresh solution of sodium citrate is added and 
platoso-ammonium chloride introduced as long as solution takes 
place. A concentrated solution of platoso-ammonium chloride 
may be kept at hand, and a small quantity of it at intervals be 
added to the bath. 

Execution of platinizing. — The objects thoroughly freed from 
grease and pickled, and, if necessary, coppered, are suspended in 
the bath heated to between 176° and 194° F. ; this temperature 
must be kept up during the entire operation. The current should 
be of sufficient strength, and the anodes placed so close to the 
objects that a liberal evolution of gas appears on the anodes. 
For platinizing large objects it is recommended to go round them, 
at a distance of 0.31 to 0.39 inch, with a hand-anode of platinum 
sheet, which should not be too small, and should be connected to the 
anode-rod. When the current has vigorously acted for 8 to 10 
minutes, the objects are taken from the bath, dried and polished. 
However, for the production of heavy deposits, for instance, upon 
points of lightning-rods, the deposit is vigorously brushed with a 
steel-wire scratch-brush or fine pumice powder. The objects are 



256 ELECTRO-DEPOSITION OF METALS. 

then once more freed from grease and returned for 10 to 15 
minutes longer to the bath to receive a further deposit of platinum 
with a weaker current, which must, however, be strong enough to 
cause the escape of an abundance of gas bubbles. The objects 
are then taken out, and after immersion in hot water, dried in 
sawdust. The deposit is then well burnished, first with the steel 
tool, and finally with the stone, whereby the gray tone disappears 
and the deposit shows the color and lustre of massive platinum 
sheet. Points of lightning-rods platinized in this manner were 
without flaw after an exposure to atmospheric influences for more 
than six years. 

Platinizing by contact. — Though a thick deposit cannot be pro- 
duced by the contact-process, Fehling's directions may here be 
mentioned as suitable for giving a thin coat of platinum to fancy 
articles. He recommends a solution of 5.64 drachms of chloride 
of platinum and 7 ozs. of common salt in 1 quart of water which 
is made alkaline by the addition of a small quantity of soda lye, 
and for use heated to the boiling point. 

If larger articles are to be platinized by contact, free them from 
grease and after pickling, and, if necessary, coppering, wrap them 
round with zinc wire or place them upon a bright zinc sheet and 
introduce them into the heated bath. All the remaining manipu- 
lations are the same as in other contact processess. 

Recovery of platinum from platinum solutions. — From not too 
large baths, precipitation of the platinum with sulphuretted 
hydrogen is the most suitable method, and preferable to evaporat- 
ing and reducing the metal from the residue. The process is as 
follows : Acidulate the platinum solution with hydrochloric acid, 
and, after warming it, conduct sulphuretted hydrogen into it. The 
metal (together with any copper present), precipitates as sulphide 
of platinum. The precipitate is filtered ofi\ dried and glowed in 
the air, whereby metallic platinum remains behind. From larger 
baths the platinum may be precipitated by suspending bright 
sheets of iron in the acidulated bath. In both cases the precipi- 
tated platinum is treated with dilute nitric acid in order to dis- 
solve any copper present. After filtering off and washing the 
pure platinum, dissolve it in aqua regia ; the solution is then 



DEPOSITION OF TIN, ZINC, LEAD, AND IRON. 257 

evaporated to dryness in the water bath, and the chloride of 
platinum thus obtained may be used in making a new bath. 



2. Deposition of Palladium. 

Properties of palladium. — Palladium when compact has a white 
color, and possesses a lustre almost equal to that of silver. Its 
specific gravity is about 12.0 ; it is malleable and ductile and may 
be fused at a white heat. In the oxyhydrogen flame it is volatil- 
ized, forming a green vapor. It is less permanent in the air than 
platinum. It is dissolved by nitric acid ; it is scarcely attacked, 
however, by hydrochloric or sulphuric acid ; hydriodic acid and 
free iodine coat it with the black palladium iodide. 

On account of the high price of its salts palladium has been 
but little used for electro-plating purposes, nor, for the same 
reason, is it likely to be more extensively employed in the future. 

According to M. Bertrand the most suitable bath consists of a 
neutral solution of the double chloride of palladium and am- 
monium which is readily decomposed by 3 Bunsen elements 
coupled one behind the other (therefore about 5.4 volts). A sheet 
of palladium is used as anode. 

A solution of palladium cyanide in potassium cyanide does not 
yield as good results as the above. 



CHAPTER XII. 



1. Deposition of Tin. 

Properties of tin. — Tin is a white, highly lustrous metal ; it 
possesses but little tenacity but has a high degree of malleability ; 
tin foil may be obtained in leaves less than ^th of a millimetre in 
thickness. Tin melts at about 446° F., and evaporates at a high 
temperature ; the fused metal shows great tendency to crystallize 
on congealing. By treating the surface of melted tin with a 
17 



258 ELECTRO-DEPOSITION OF METALS. 

dilute acid, the crystalline structure appears as designs {moire 
metallique), resembling the ice-flowers on frosted windows. 

Tin remains quite constant even in moist air, and resists the 
influence of an atmosphere containing sulphuretted hydrogen. 
Strong hydrochloric acid quickly dissolves tin on heating, evolving 
hydrogen and forming stannous chloride. Dilute sulphuric acid 
has but little action on the metal ; when heated with concentrated 
sulphuric acid sulphur dioxide is evolved. Dilute nitric acid dis- 
solves tin in the cold without evolution of gas ; concentrated nitric 
acid acts vigorously upon the metal, whereby oxide of tin, which 
is insoluble in the acid, is formed. Alkaline lyes dissolve the 
metal to sodium stannate, hydrogen being thereby evolved. 

Tin baths. — The bath used by Roseleur for tinning with the 
battery works very well, and is composed as follows : I. Pyro- 
phosphate of soda 3.5 ozs., tin salt (fused) 0.35 oz., water 10 
quarts. To prepare the bath dissolve the pyrophosphate of soda 
in 10 quarts of rain water, bring the tin salt in a small linen bag 
into the solution, and move the bag to and fro until its contents 
are entirely dissolved. 

Objects of zinc, copper, and brass are directly tinned in this 
bath with a current of slight tension. Articles of iron and steel 
are first coppered or preliminarily tinned in a bath prepared ac- 
cording to formula VI, the deposit of tin being then augmented 
in bath I with the battery current. Cast-tin anodes as large as 
possible are used, which, however, will not keep the content of tin 
in the bath constant. It is therefore necessary from time to time to 
add tin salt, which is best done by preparing a solution of 3.5 ozs. of 
pyrophosphate of soda in 1 quart of water, and introducing into the 
solution tin salt as long as the latter dissolves clear. Of this tin 
essence add to the bath more or less, as may be required, and also 
augument the content of pyrophosphate of soda, if notwithstand- 
ing the addition of tin salt, the deposition of tin proceeds 
sluggishly. 

Though the bath composed according to formula I suflices for 
most purposes, an alkaline tin bath, first proposed by Eisner and 
later recommended by Maistrasse, Fearn, Birgham, and others, 
with or without addition of potassium cyanide, may be mentioned : 



DEPOSITION OF TIN, ZINC, LEAD, AND IRON. 259 

II. Crystallized tin salt 0.7 oz., water 1 quart, and potash lye 
of 10° Be., until the precipitate formed dissolves. 

As seen from the formula the solution of tin salt is compounded 
with potash lye of the stated concentration (or with a solution of 
1 oz. of pure caustic potash in water), until the precipitate of 
stannous hydrate again dissolves. 

Some operators recommend the addition of 0.35 oz. of potas- 
sium cyanide to the solution. 

Without potassium cyanide the bath requires 3.75 to 4 volts, 
and with it 3.5 volts. 

In testing Salzede's bronze bath (p. 199), it was found to yield 
quite a good deposit of tin directly upon cast-iron, and it was suc- 
cessfully used for this purpose by omitting the cuprous chloride 
and using 14.11 drachms of stannous chloride, so that the com- 
position became as follows : — 

II a. 98 per cent, potassium cyanide 3.5 ozs., carbonate of 
potassium 35 J ozs., stannous chloride 14.11 drachms, water 10 
quarts. With 4 volts a heavy deposit was rapidly obtained. 

Management of tin baths. — Tin baths should not be used at a 
temperature below 68° F. ; they require (formula? I and II), 
according to their composition, a current of 2 to 3 volts, so that 
two Bunsen elements coupled one after the other suffice for all 
purposes. Too strong a current causes a pulverulent reduction of 
the tin which does not adhere well, while with a suitable current- 
strength quite a dense and rcguline deposit is obtained. Cast-tin 
plates with as large a surface as possible are used as anodes. 
The choice of the tin salt exerts some influence upon the color of 
the tinning. By using, for instance, crystallized tin salt, which 
is always acid, in preparing the bath according to formula I, a 
beautiful white tinning with a bluish tinge is obtained, which, 
however, does not adhere as well as that produced with fused tin 
salt. Again the latter yields a somewhat dull gray layer of tin, 
and, therefore, the effects of the bath will have to be corrected 
by the addition of one or the other salt. 

As previously mentioned, iron and steel objects are best sub- 
jected to a light preliminary tinning by boiling in the bath VI ; 
however, instead of this preliminary tinning, they may first be 
electro-coppered, and after scratch-brushing the copper deposit, 
brought into the tin bath. 



260 ELECTRO-DEPOSITION OF METALS. 

When the action of the bath becomes sluggish it has to be re- 
freshed (for formula I), by the addition of tin salt and pyrophos- 
phate of soda, or (for formula II), by the addition of potash lye 
and tin salt. 

From what has been said it will be clear that the execution of 
tinning is simple enough. After freeing from grease and pickling 
the objects are brought into the bath and tinned with a weak cur- 
rent. For heavy deposits of tin the objects are frequently taken 
from the bath, and the deposit is thoroughly brushed with a brass 
scratch-brush, not too hard, and moistened with dilute sulphuric 
acid (1 part acid of 66° Be. to 25 water), when, after rinsing in 
water, the articles are returned to the bath. If, with the use of 
too strong a current the color of the deposit is observed to turn 
a dark dull gray, scratch-brushing must be repeated. When the 
tinning is finished the articles are brushed with a brass scratch- 
brush and decoction of soap root, then dried in sawdust and 
polished with fine whiting. 

Tinning by contact and boiling. — For tinning by zinc contact 
in the boiling tin bath the following solutions may be recom- 
mended : — 

III. According to Gerhold : Pulverized tartar and alum, of 
each, 3.5 ozs., fused stannous chloride 14 drachms, rain water 
10 quarts. 

IV. According to Roseleur : Potassium pyrophosphate 7 ozs., 
crystallized stannous chloride (tin salt), 11 drachms, fused 
stannous chloride 2.8 ozs., rain water 10 quarts. 

V. According to Roseleur for tinning by immersion : Potassium 
pyrophosphate 5.6 ozs., fused stannous chloride 1.23 ozs., rain 
water 10 quarts. 

Formula? Ill and IV yield good results. For tinning by con- 
tact, heat the bath to boiling and suspend the clean and pickled 
objects in contact with pieces of zinc, or, better, wrapped around 
with zinc wire spirals, care being had to from time to time shift 
them about to prevent staining. Large baths which cannot be 
readily heated are worked cold, the objects being covered with a 
large zinc plate ; in the cold bath the formation of the tin deposit 
requires, of course, a longer time. By using the electric current 
the deposit can be made as heavy as desired. By immersion in 
the bath prepared according to formula V, zinc can only be 



ZINC, LEAD, AND IRON. 261 

coated with a very thin film of tin, which, however, can be made 
as heavy as desired by the nse of a battery. 

For tinning by contact in a cold bath, Zilken has patented the 
following solution : Dissolve with the aid of heat in 100 quarts 
of water, tin salt 7 to 10.5 ozs., pulverized alum 10.5 ozs., com- 
mon salt 1 5f ozs., and pulverized tartar 7 ozs. The cold solution 
forms the tin bath. The objects to be tinned are to be wrapped 
round with strips of zinc. Duration of the process 8 to 10 
hours. 

Tinning solution for iron and steel articles. — VI. Crystallized 
ammonium-alum 7 ozs., crystallized stannous chloride 2.8 drachms, 
fused stannous chloride 2.8 drachms, rain water 10 quarts. Dis- 
solve the ammonium-alum in the hot water, and when dissolved 
add the tin salts. The bath is to be used boiling hot, and kept 
at its original strength by an occasional addition of tin salt. The 
clean and pickled iron objects being immersed in the bath 
become in a few seconds coated with a firmly adhering film of 
tin of a dead white color, which may be polished by scratch- 
brushing, or scouriug with sawdust in the tumbling drum. Tin- 
ning by boiling in this bath is the most suitable preparation for 
iron and steel objects which are to be provided with a heavy 
electro-deposit of tin. To be entirely sure of success it is recom- 
mended to thoroughly scratch-brush the objects, then to return 
them once more to the bath, and finally suspend them in a bath 
composed according to formula I or II. 

A tinning solution for small brass and copper articles (pins, eyes, 
hooks, etc.), consists of a boiling solution of: Pulverized tartar 
3.5 ozs., stannous chloride (tin salt) 14.11 drachms, water 10 
quarts. After heating the bath to the boiling point immerse the 
objects to be tinned in a tin sieve or in contact with pieces of 
zinc ; frequent stirring with a tin rod shortening the process. 

Another solution, given by Bottger, also yields good results. 
Dissolve oxide of tin by boiling with potash lye, and place the 
copper or brass objects to be tinned in the boiling solution in 
contact with tin shavings. 

Eisner's bath yields equally good results. It consists of a 
solution of equal parts of tin salt and common salt in rain water. 
The manipulation is the same as given above. 



262 ELECTRO-DEPOSITION OF METALS. 

A characteristic method of tinning by Stolba is as follows : 
Prepare a solution of 1.75 ozs. of tin salt, and 5.64 drachms of 
pulverized tartar in 1 quart of water ; moisten with this solution 
a small sponge and dip the latter into pulverulent zinc. By 
then rubbing the thoroughly cleansed and pickled articles with 
the sponge they immediately become coated with a film of tin. 
To obtain uniform tinning, the sponge must be repeatedly dipped 
now into the solution and then into the zinc pow r der, and the rub- 
bing continued for a few minutes. 

For coloring and platinizing tin, see special chapter. 

2. Deposition of zinc. 

Properties of zinc. — Zinc is a bluish-white metal possessing 
high metallic lustre. It melts at 770° F. At the ordinary 
temperature zinc is brittle, but is malleable at between 212° and 
300° F., and can be rolled into sheet; at 392° F. it again 
becomes brittle and may be readily reduced to powder. The 
specific gravity of zinc varies from about 6.86 to 7.2. When 
strongly heated in air or in oxygen it burns with a greenish- 
white flame producing dense white fumes of the oxide. 

In the air, zinc loses its lustre and becomes coated with a gray 
layer of oxide which protects the metal beneath from further 
oxidation. Pure zinc dissolves slowly in the ordinary mineral 
acids, but the commercial article containing foreign metals is 
rapidly attacked with production of hydrogen. 

Zinc being a very electro-positive metal precipitates most of the 
heavy metals from their solutions, especially copper, silver, lead, 
antimony, arsenic, tin, cadmium, etc., this being the reason why in 
dissolving impure zinc, the admixed metals do not pass into solu- 
tion so long as zinc in excess is present. Caustic alkalies also 
dissolve zinc with formation of an oxide and free hydrogen, 
especially when it is in contact with a more electro-negative metal. 

Zinc baths. — Though most metals can be readily coated with 
a firmly adhering thin layer of zinc by the wet way and with the 
aid of the battery, electro-deposited zinc in comparison with that 
deposited by " galvanizing" is much inferior as a protective coat- 
ing. It may, nevertheless, be useful to give the composition of 



DEPOSITION OF TIN, ZINC, LEAD, AND IRON. 263 

some baths which have stood the test, as well as the most approved 
directions for zincking. 

I. Sulphate of zinc (white vitriol) 2.8 ozs., ammonium sul- 
phate If ozs., sal ammoniac 11 drachms, water 1 quart. Dissolve 
the salts in the heated water aad use the bath at 68° F. The 
current-strength should only be slightly greater than necessary 
for the decomposition of the bath ; the current of two Bunsen 
elements coupled one after the other is quite too strong and 
must, • therefore, be correspondingly weakened by the resistance 
board. 

As anodes rolled zinc sheets of not too small dimensions are 
to be used. This bath is suitable for heavily zincking objects 
(sheets, plates) of wrought- and cast-iron steel, and all other metals, 
but not for zincking hollow articles if anodes cannot at equal 
distances be placed around them. The most suitable tension is 
2.8 to 3 volts. 

II. Caustic potash 2 ozs., chloride of zinc 5J drachms, sal 
ammoniac 11 drachms, water 1 quart. Dissolve the caustic 
potash in one-half of the water, and the chloride of zinc and 
sal ammoniac in the other half, and mix the solution with stir- 
ring. The result is a clear fluid which requires a current of 2.5 
to 3 volts for its decomposition. Zinc sheets are also used as 
anodes. In this bath the deposit upon hollow objects proceeds 
better than in the preceding, though frequent turning of the 
articles is necessary. 

III. Alum 3J ozs., hydrated oxide of zinc 5J drachms, water 
1 quart. Dissolve 14 drachms of sulphate of zinc in 1 pint of 
water and carefully add potash lye until a further drop of it no 
longer produces a precipitate. Since potash lye dissolves the hy- 
drated oxide of zinc an excess has to be avoided. The precipitate 
is filtered off, washed with water and the hydrated oxide of zinc, 
while still moist, is heated together with the solution of 3 \, ozs. 
of alum in 1 quart of water, whereby it is completely dissolved. 
This bath requires a current of 3 to 3.5 volts. 

IV. Sulphate of zinc (white vitriol) 2.8 ozs., water 1 quart, 
and potash lye sufficient to redissolve the precipitated hydrated 
oxide of tin. This bath also works quite well, and requires from 
2.75 to 3 volts and 1.5 amperes per 15 J square inches. 



264 ELECTRO-DEPOSITION OF METALS. 

Solution of cyanide of zinc in potassium cyanide may also be 
used for zineking, such bath having been warmly recommended 
by some authors. However, the production of deposits of some 
thickness requires a long time, and the deposit itself shows a 
tendency to peeling off. # 

Execution of zineking. — Next to thorough cleansing and pick- 
ling the objects, especially iron castings, and regulating the cur- 
rent, electro-zincking depends on the frequent turning and 
changing of the objects in the bath, since the deposit is chiefly 
formed upon the portions nearest to the anodes, and not at all, or 
with difficulty, upon the portions away from the anodes. If, not- 
withstanding frequent changing, some portions do not acquire a de- 
posit, recourse must be had, as in nickeling, to the hand anode. 
Next to frequently changing the articles in the bath it is recom- 
mended to scratch-brush them several times, especially if heavy 
deposits are to be produced. It is also advisable to somewhat 
heat the baths if possible. 

It is of advantage to superficially zinc iron objects by a com- 
bined process of contact and boiling, and then to augment the 
layer of zinc in the bath. 

After thorough scratch-brushing with a steel brush, not too 
hard, and a decoction of soap root, the zincked objects are rinsed 
in lime water, then plunged into hot water and dried in sawdust ; 
polishing is effected upon soft cloth bobs with Vienna lime and oil. 

For zineking iron by contact quite a concentrated solution of 
chloride of zinc and sal ammoniac in water only is suitable, in 
which the objects are placed in contact with large surfaces of 
zinc. 

To coat brass and copper with a bright layer of zinc proceed 
as follows : Boil commercial zinc-gray, i. e., very finely divided 
metallic zinc, several hours with concentrated solution of caustic 
soda. Then immerse the articles to be zincked in the boiling 
fluid when, by continued boiling, the articles will, in a short time, 
become coated with a very bright layer of zinc. When a copper 
article thus coated with zinc is carefully heated in an oil bath to 
between 248° and 284° F., the zinc alloys with the copper, form- 
ing a sort of bronze similar to tombac. 

Weil zincks copper and coppered objects by immersing them 



DEPOSITION OF TIN, ZINC, LEAD, AND IRON. 265 

in a boiling concentrated solution of caustic potash in contact 
with zinc. The coating thus obtained is said to be adherent and 
brilliant. 

For coloring and platinizing zinc, see special chapter. 

Zinc alloys. — The production of the principal zinc alloy, brass, 
by the galvanic method, having already been mentioned, and also 
that of a zinc-nickel-copper alloy (German silver), it remains to 
give an alloy of zinc with tin which can be produced by the use 
of the battery. 

A suitable bath for depositing this alloy consists of: Chloride 
of zinc 6} drachms, crystallized stannous chloride 9 drachms, 
pulverized tartar 9 drachms, pyrophosphate of soda 2} drachms, 
water 1 quart. Dissolve the salt at a boiling heat, and filter the 
cold solution, when it is ready for use. For anodes cast plates of 
equal parts of tin and zinc are used. 

3. Deposition of Lead. 

The properties of lead only interest us in so far as it being less 
attacked by most mineral acids than other metals, objects have 
been coated with it in order to protect them against the action of 
such agents. For decorative purposes electro-deposits of lead are 
not used and those as a protection against chemical influences can- 
not be produced of sufficient thickness for that purpose. 

Lead baths. — I. Dissolve, by continued boiling, caustic potash 
1.75 ozs. and finely pulverized litharge 0.17 oz. in 1 quart of 
water. 

II. According to Watt the following solution is used : Acetate 
of lead 0.17 oz., acetic acid 0.17 oz., water 1 quart. 

The bath prepared according to formula I deserves the prefer- 
ence. 

Lead baths require anodes of sheet lead or cast-lead plates, a 
very weak current, and in order to produce a dense deposit of some 
thickness, the objects have to be frequently scratch-brushed. Iron 
is best previously coppered. Superoxide of lead being separated 
upon the anodes they have to be frequently cleansed with a scratch- 
brush. The formation of superoxide of lead is utilized for the 



266 ELECTRO-DEPOSITION OF METALS. 

production of the so-called Nobili's rings (electrochromy), which 
will be mentioned below. 

Leading by contact is effected by suspending the objects, 
thoroughly freed from grease, in the boiling solution prepared 
according to formula I, in contact with a piece of tin. 

Nobili's rings (iridescent colors, electrochromy). — The separation 
of superoxide of lead upon the anodes or upon objects suspended 
as anodes, produces superb effects of colors. For the production 
of such colors, a bath is prepared by boiling for half an hour 
3J- ozs. of caustic potash, 14 drachms of litharge, and 1 quart of 
water. The operation is as follows : Suspend the articles, care- 
fully freed from grease and pickled, to the anode-rods, and with 
a weak current introduce in the lead solution a thin platinum 
wire, connected with the object-rod by flexible copper wire, with- 
out however touching the article. The latter will successively 
become colored with various shades — yellow, green, red, violet, 
and blue. By the continued action of the current, these colors 
pass into a discolored brown, which also appears in the begin- 
ning if the current is too strong, or the platinum wire be immersed 
too deep. Such unsuccessful coloration has to be removed by 
rapidly dipping in aqua fortis, and after rinsing in water, the 
article is to be again suspended in the bath. For not too large 
surfaces which are to be colored, a medium-sized Bunsen element 
is, as a rule, sufficient, if the platinum wire be immersed about 
f inch. 

Colors of all possible beautiful contrasts may be obtained by 
perpendicularly placing between the objects to be colored and the 
platinum wire, a piece of stout parchment paper, or providing 
the latter with many holes or radial segments. 

4. Deposition of Iron (Steeling). 

The principal practical use of the electro-deposition of iron, is 
to cover printing plates of softer metals with a coating of " steel," 
to increase their wearing qualities. However, the steeling of 
printing plates has no advantage over nickeling or cobalting, 
which has lately been introduced with the best success. 



DEPOSITION OF TIN, ZINC, LEAD, AND IRON. 267 

Steel baths. — I. According to Varrentrapp : Pure green vitriol 
4} ozs., sal ammoniac 3J ozs.^ water 1 quart. Boil the water 
for j- hour to remove all air, and after cooling, add the green 
vitriol and sal ammoniac. By the action of the air, and the 
oxygen appearing on the anodes, this bath is readily decomposed, 
insoluble basic sulphate of iron being separated as a delicate 
powder, which has to be frequently removed from the fluid by 
filtering. To decrease decomposition, the double sulphate of iron 
and ammonium, which can be more readily obtained pure and free 
from oxide, may be used. 

II. Sal ammoniac 3| ozs., water 1 quart. This neutral solu- 
tion of sal ammoniac may be made into an iron bath by hanging 
into it iron sheets as anodes, suspending an iron or copper plate 
as cathode, and allowing the current to circulate until a regular 
separation of iron is attained, which is generally the case in 5 to 
6 hours. Though a separation of hydrated oxide of iron also 
takes place in this bath, it is in a less degree than in that pre- 
pared according to formula I. For the production of not too 
heavy a deposit of iron, some operators claim to have obtained 
the best results with this bath. 

For the production of electrotypes in iron the following baths 
(III and IV) are most suitable : — 

III. Ammonia ferrous sulphate If ozs., water 1 quart. The 
solution must be kept absolutely neutral, which according to 
Klein's suggestion is, on the one hand, to be attained by the use 
of large anode-surfaces, and on the other, by su spending in the 
bath a copper plate and connecting it with the anodes. It would 
seem more advantageous to maintain the neutrality of the bath 
by suspending in it small bags filled with carbonate of magnesia. 

A steel bath highly recommended by Klein consists of a solu- 
tion of equal parts of green vitriol and sulphate of magnesia, 
which is kept neutral by bags filled with carbonate of magnesia 
suspended in the fluid. The most suitable concentration of the 
solution corresponds to a specific gravity of 1.55 ; and according 
to the most recent experiments, the current-density should at the 
utmost amount to 0.02 ampere per 15 J square inches, with a 
distance of 1 J inches of the anodes from the plate, this distance 
to be gradually increased. 



268 ELECTRO-DEPOSITION OF METALS. 

For decorative purposes, a deep black deposit of iron may, 
according to " La Metallurgie," be produced as follows : Dissolve 
as large a quantity of steel filings as possible in 50 quarts of com- 
mercial hydrochloric acid. The saturation of the solution is 
recognized by a sediment, which no longer dissolves, being formed 
on the bottom of the vessel. Then add 2 lbs. of white arsenic, 
and vigorously stir the mixture. The arsenic dissolves very 
slowly, but the bath cannot be considered finished until all of it 
is dissolved, and the color obtained by means of the bath is the 
deeper, the more complete the solution of the arsenic. The* 
articles to be treated are connected to the negative pole of the 
battery, iron and carbon plates serving as anodes. For a bath of 50 
quarts, two Bunsen elements about 7f inches high are required, and 
the bath being very acid, the articles must be connected with the 
battery prior to immersion. Upon copper and brass, the deposit 
is directly produced, but iron articles being attacked by the bath, 
are first provided with a coat of nickel. The deposit of iron upon 
this nickel coating is very beautiful, and has been designated as 
" black nickeling." The coating must, of course, be protected 
from oxidation by a colorless lacquer. 

Management of iron baths. — As previously mentioned, the inso- 
suble precipitate from time to time formed in the bath, has to be 
removed by filtration. This precipitate is, however, very delicate, 
and when stirred up might settle upon the objects and prevent 
the adherence of the deposit. It is, therefore, advisable to use 
for steel baths, vats of much greater depth than correspond to 
the height of the objects, whereby the stirring up of the sediment 
in suspending the objects in the bath is best avoided. The baths 
must be kept thoroughly neutral, which may be effected in vari- 
ous ways. One method has already been mentioned in connec- 
tion with formula III ; another method which has been used with 
decided success, consists in precipitating, with excluding the air 
as much as possible, a solution of pure green vitriol with ammo- 
nium carbonate, quickly filtering off the ferrous carbonate, wash- 
ing the latter once or twice in cold water previously boiled, 
stirring it, while moist, into the bath, and allowing it to settle 
for one hour. 



DEPOSITION OF ANTIMONY, ARSENIC, ALUMINIUM. 269 

Execution of steeling. — Only the manipulations for the produc- 
tion of thin deposits will here be discussed. The production of 
heavy galvanoplastic deposits of iron will be explained later on 
under " Galvanoplasty." 

The clean and pickled objects are coated in the baths accord- 
ing to formulae I and II, with a current of 1 to 1.25 volts, and 
the anodes at a distance of 3f to 4} inches, after which the cur- 
rent is reduced to 0.75 or 1 volt. To produce iron deposits of 
any kind of thickness, the escape of the hydrogen bubbles which 
settle on the objects must be promoted by frequent blows with 
the finger upon the object-rod. As anodes iron sheets of a large 
surface freed from scale by pickling are to be used. When steel- 
ing is finished, the articles are thoroughly rinsed, then plunged 
into very hot water, and after drying in sawdust, placed for 
several hours in a drying chamber heated to about 212° F., to 
expel all moisture from the pores. 

Steeling by contact is readily effected by touching the objects 
with zinc, best in a bath prepared according to formula I. 



CHAPTER XIII. 

ALUMINIUM. 
1. Deposition of Antimony. 

Properties of antimony. — Electro-deposited antimony possesses 
a gray lustre, while native, fused antimony shows a silver- white 
color. Antimony is hard, very brittle, and may easily be reduced 
to powder in a mortar. It melts at 842° F., and at a strong red 
heat takes fire and burns with a white flame, forming the trioxide. 
Its density is 6.8. It is permanent in the air at ordinary temper- 
atures. Cold, dilute and concentrated sulphuric acid have no 
effect upon antimony, but the hot concentrated acid forms sul- 
phide of antimony. By nitric acid the metal is more or less 
energetically oxidized according to the strength and temperature 
of the acid. 



270 ELECTRO-DEPOSITION OF METALS. 

Antimony baths. — Electro-depositions of antimony are but sel- 
dom made use of in the industries, though they are very suitable 
for the production of contrasts in decorating. Gore discovered 
the explosive power of depositions of antimony chloride, or of 
antimony containing hydrochloric acid. According to Gore, a 
bath consisting of tartar emetic 3 ozs., hydrochloric acid 4J ozs., 
tartaric acid, 3 ozs., and water 1 quart, yields a gray crystalline 
deposit of antimony. This bath requires a current of about 3 
volts. The deposit possesses the property of exploding when 
scratched with a hard object. The explosion of the deposit is 
caused by a content of chloride of antimony. Bottger found 3 
to 5 per cent, of chloride of antimony in the deposit, and Gore 
6 per cent. A similar explosive deposit is obtained by electro- 
lyzing a simple solution of chloride of antimony in hydrochloric 
acid (liquid butter of antimony, liquor stibii chlorati) with the 
current. 

A lustrous non-explosive deposit of antimony is obtained by 
boiling 4.4 ozs. of carbonate of potash, 2.11 ozs. of pulverized 
antimony sulphide and 1 quart of water, for 1 hour, replacing the 
water lost by evaporation, and filtering. Use the bath boiling 
hot, employing cast antimony plates or platinum sheets, as anodes. 

Another antimony bath may be prepared by dissolving freshly 
precipitated sulphide of antimony with an excess of sulphide of 
ammonia. It yields a very lustrous and adherent deposit of anti- 
mony, which, in 6 to 8 minutes, is of sufficient thickness to bear 
polishing with Vienna lime upon rapidly revolving cloth disks. 
An unpleasant feature of this bath is that during the plating pro- 
cess much sulphur is separated, which renders the bath turbid, 
so that it has to be frequently filtered. With the use of platinum 
anodes, this separation of sulphur is, of course, still greater than 
with antimony anodes. 

2. Deposition of Arsenic. 

Proper-ties of arsenic. — Arsenic has a gray-white color, a strong 
metallic lustre, is very brittle, and evaporates at a red heat. In 
dry air arsenic retains its lustre, but soon turns dark in moist air. 
It is scarcely attacked by dilute hydrochloric and sulphuric acids, 



DEPOSITION OF ANTIMONY, ARSENIC, ALUMINIUM. 271 

while concentrated sulphuric acid as well as nitric acid oxidizes it 
to arsenious acid. If caustic alkalies are fused together with 
arsenic, a portion of the latter is converted into alkaline arsenate. 
Arsenic baths. — Deposits of arsenic are more frequently used 
than autirnoiiy deposits for decorative purposes ; for instance, to 
color gray the dead back ground of brassed lamp legs, cans, etc., 
while the prominent portions are bright brass. A solution suit- 
able for depositing arsenic upon all kinds of metals is as follows : — 

I. Pulverized arsenious acid If ozs., crystallized pyrophosphate 
of soda 0.7 oz., 98 per cent, potassium cyanide If ozs., water 1 
quart. 

Dissolve the pyrophosphate of soda and potassium cyanide in 
the cold water, and after adding, with stirring, the arsenious acid, 
heat until the latter is dissolved. In heating, fumes containing 
prussic acid escape, the inhalation of which must be carefully 
avoided. The bath is used warm, and requires a vigorous cur- 
rent of at least 4 volts, so that, at the least, 3 Bunsen elements 
have to be coupled for tension. After suspending the objects they 
are first colored black-blue, the color passing with an increased 
thickness of the deposit into pale blue, and finally into the true 
arsenic gray. Platinum sheets or carbon plates are to be used as 
anodes. 

Instead of a bath prepared according to formula I, a solution 
of the following composition may be used : — 

II. Sodium arsenate If ozs., 98 per cent, potassium cyanide 
0.8 oz., water 1 quart. Boil the solution for half an hour, then 
filter and use it at a temperature of at least 167° to 176° P., 
with a strong current ; it yields a good deposit. 

Large baths, to be used cold, must be more concentrated, and 
require a stronger current than hot baths. 

When the baths begin to work irregularly and sluggishly, they 
have to be replaced by fresh solutions. 

In the execution of deposits of arsenic and antimony the same 
rules are to be observed as for the other electro-plating processes. 

Deposits of antimony and arsenic by contact and immersion are 
much used for coloring brass and copper, as well as iron (brown- 
ing of gun -barrels) and silver. Most frequently a warm solution 
of antimony trichloride (the butter of antimony of commerce) 



272 ELECTRO-DEPOSITION OF METALS. 

in hydrochloric acid is used for this purpose, in which the clean 
and pickled brass articles acquire a coating of a steel-gray color 
with a bluish tinge. By using instead a hot mixture of chloride 
of arsenic with a small quantity of water, a steel-gray color with- 
out a bluish tinge is obtained. 

By immersing brass in a solution of 20 parts by weight of 
arsenious acid, 40 of hydrochloric acid, 800 of water, and 10 of 
sulphuric acid, heated to between 122° and 140° F., it becomes 
black by the separation of pulverulent arsenic ; after rinsing in 
water and drying the coat adheres quite well. By contact with 
zinc the deposit is obtained in a shorter time and adheres better. 

3. Deposition of Aluminium. 

Properties of aluminium. — Aluminium is a white silvery metal 
with an almost imperceptible bluish tinge. It is extremely light, 
the specific gravity being only 2.58, is very malleable and ductile, 
takes a high polish, and is not liable to tarnish in the air. It 
melts at about 1300° F. Its principal common impurities are 
iron and silicon. 

Aluminium baths. — Aluminium does not seem to possess any 
qualities that would make it advantageous as an electro-deposit 
upon other metals. Many solutions have been proposed which it 
was claimed should give good deposits of the metal, but have been 
found by various experimenters to be worthless. We, therefore, 
confine ourselves to giving only a few solutions which are claimed 
to give good results. 

I. Bertrand states that he has deposited aluminium upon a plate 
of copper in a solution of the double chloride of aluminium and 
ammonium by using a strong current from three Bunsen elements, 
the bath being worked at 140° F. 

II. Goze's process. — Mr. Goze obtained a deposit of aluminium 
by the single cell method from a dilute solution of the chloride. 
The liquid was placed in a jar in which was immersed a porous 
cell containing dilute sulphuric acid ; an amalgamated zinc plate 
was immersed in the acid solution and a plate of copper in the 
chloride solution, the two metals being connected by a copper 
conducting wire. At the end of some hours the copper plate 



GALVANOPLASTY. 273 

became coated with a lead-colored deposit of aluminium which, 
when burnished, presented the same degree of whiteness as 
platinum and did not appear to tarnish readily when immersed 
in cold water or exposed to the atmosphere, but was acted upon 
by dilute sulphuric and nitric acids. 

III. The following formula is given by Mr. Herman Reinbold, 
who states that it yields excellent results : Dissolve 50 parts by 
weight of alum in 300 of water and to this add 10 parts of 
aluminium chloride. The solution is to be heated to 200° F., 
and, when cold, 39 parts of potassium cyanide are to be added. 
A feeble currrent should be used. 



The electro-deposition of tungsten, cadmium, and bismuth 
having, up to the present time, attained no practical importance, 
its discussion may be omitted. 



CHAPTER XIY. 

GALVANOPLASTY (REPRODUCTION). 

By galvanoplasty proper is understood the production, with the 
assistance of the electric current, of copies of articles of various 
kinds, true to nature, and of sufficient thickness to form a resisting 
body, which may be separated from the object serving as a mould. 

Copper is the most suitable metal for galvanoplastic processes, 
that which is precipitated by electrolysis showing the following 
valuable properties : It may be precipitated chemically pure, and 
in this state is less capable of change than ordinary commercial 
copper or the ordinarily used copper alloys, its strength of ex- 
tension being 20 per cent, greater than that of melted copper ; its 
hardness is also greater than that of melted copper, while its 
specific gravity (8.85) lies between that of cast and rolled copper. 

The physical properties of copper deposited by electrolysis are 
dependent on the condition of the bath as well as on the intensity 
and tension of the working current. The bath used for precipi- 
tating the copper is in all cases a solution of blue vitriol. Smee 
18 



274 ELECTRO-DEPOSITION OF METALS. 

had already proved by experiments that copper is obtained as a 
more tenacious and fine-grained deposit when the current-strength 
is as great as possible, without, however, evolution of hydrogen 
taking place, while copper in pulverulent sandy form is obtained 
with a current-strength that liberates hydrogen, and in coarsely 
crystalline form when the current-strength is very slight. 

At a more recent period, von Hiibl instituted a series of 
systematic experiments for the determination of the conditions 
under which deposits with different physical properties are ob- 
tained. Hiibl worked with 5 per cent, neutral, and 5 per cent, 
acid, solutions of copper, as well as with 20 per cent, neutral, and 
20 per cent., acid solutions. The neutral solutions were prepared 
by boiling blue vitriol solution with carbonate of copper in ex- 
cess, and the acid solutions by adding 2 per cent, of sulphuric acid 
of 6Q° Be. The result was that in the neutral 5 per cent, solutions 
less brittle deposits were obtained with a small current-density, 
than in a more concentrated solution, though the appearance of 
the deposits was the same. The experiments with acidulated 
baths confirmed the fact that free sulphuric acid promotes the 
formation of very fine-grained deposits even with very slight cur- 
rent-densities, and it appears that the brittleness of copper de- 
posited from acid baths is influenced less by the concentration 
than by the current- density used. 

The processes used in galvanoplasty may be arranged into 
two classes, viz., the deposition of copper with, or loithout the use 
of external sources of current, the first comprising galvanoplastic 
deposits produced by means of the single cell apparatus, and the 
other those by the battery or dynamo machine. 

1 . Galvanoplastic Deposition in the Cell Apparatus. 

The cell apparatus consists of a vessel containing blue vitriol 
solution kept saturated by a few crystals of blue vitriol placed in 
a muslin bag or a small perforated box of wood, stoneware, etc. 
In this vessel are placed round or square porous clay cells (dia- 
phragms) which contain dilute sulphuric acid and a zinc plate, the 
zinc plates being connected with the other and with the objects 
to be moulded — which may be either metallic or made conductive 
by graphite — by copper wire, or copper rods. The objects to be 



GALVANOPLASTY. 



275 



moulded play the same role as the copper electrode in a Daniell 
element, and the cell apparatus is nothing else but a species of 
Daniell element in which the internal, instead of an external, cur- 
rent is utilized. As soon as the circuit is closed by the contact of 
the objects to be moulded with the zinc of the porous cell, the 
electrolytic process begins ; the zinc is oxidized by the oxygen and 
with the sulphuric acid forms zinc sulphate (white vitriol), while 
the copper is reduced from the blue vitriol solution and deposited 
in a homogeneous layer upon the articles to be moulded. 

A simple apparatus, frequently used by amateurs for moulding 
medals, reliefs, etc., is shown in Fig. 89. 

Fig. 89. 




In a cylindrical vessel of glass or stone-ware filled with satu- 
rated blue vitriol solution, is placed a porous clay cell, and in the 
latter a zinc cylinder projecting about 0.039 to 0.079 inch above 
the porous clay cell. To the zinc is soldered a copper ring, as 
plainly shown in the illustration. The clay cell is filled with 
dilute sulphuric acid (1 acid to 30 water) to which some amalga- 
mating salt may suitably be added. The articles to be moulded 
are suspended to the copper ring, care being had to have the 
surfaces which are to be covered, near and opposite to the cell. 
To supplement the content of copper, small linen or sail-cloth 
bags filled with blue vitriol are attached to the upper, edge of the 
vessel. 



276 



ELECTRO-DEPOSITION OF METALS. 



Large apparatus. — To cover large surfaces, use large, square 
vats of stone-ware, or of wood lined with lead, gutta-percha or 
another substance unacted upon by the bath. For baths up to 
three feet long stone- ware vats are to be preferred. 

Fig. 90 shows the French form of cell apparatus. In the middle 
of the vat, and in the direction of its length, is disposed a row of 

Fig 90. 




nnnii nnmmnmiiiiim iiimniiimiiin»ii iininiiiiimiiiiiiiiiiiiiiiiiiiiHiiiiii iiiHiiiiiiiHiiiiiiiiiiiMiiiiiiiii|iii«iiiiiiiiiiiiiiiiiiiiiiiiiiiii 




cylindrical cells, close to each other, each provided with its zinc 
cylinder. A thin metallic ribbon is connected with all the bind- 
ing screws of the cylinder, and is in contact at its extremities 
with two metallic bands on the ledges of the depositing vat. The 
metallic rods supporting the moulds are in contact with the 
metallic bands of the ledges, and, therefore, in connection with 
the zincs. 

The German form of cell apparatus is shown in Fig. 91. It 
is provided with long, narrow, rectangular cells of a correspond- 
ingly greater height than the column of fluid. 

Across the vat are placed three conducting rods connected with 
each other by binding screws and copper wire. To the centre rod 
which lies over the cells are suspended the zinc plates by means 
of a hook, while the two outer rods serve for the reception of the 
moulds. 



GALVANOPLASTY. 



277 



The size of the zinc surfaces in the simple apparatus should be 
about equal to that of the surfaces to be moulded if dilute sul- 
phuric acid (1.30) is to be used. For particulars see " Execution 
of the Galvanoplastic Deposition of Copper." 




The copper bath for the cell apparatus consists best ot a mode- 
rately saturated solution of pure blue vitriol, free from iron, in 
water free from lime, and should show about 18° to 20° Be., a 
bath of 100 quarts requiring about 20 to 24 lbs. of blue vitriol. 
The following table gives the approximate content of pure crys- 
tallized blue vitriol at different degrees Be., and at 59° F. 



Degrees, Be. 


Weight by volume. 


The solution contains 
crystallized blue vitriol. 




5° .... 


1.035 


5 


aer cent. 




10° 










1.072 


11 


" 




12° 










1.088 


13 


ti 




15° 










1.113 


17 


(< 




16° 










1.121 


18 


u 




17° 










1.130 


19 


It 




18° 










1.13S 


20 


(< 




19° 










1.147 


21 


u 




20° 










1.157 


23 


(I 




21° 










1.166 


24 


a 




22° 










1.176 


25 


a 



While to a copper bath working with the use of an external 
source of current more or less sulphuric acid is added, according 



278 ELECTRO-DEPOSITION OF METALS. 

to requirement. Baths in the single cell apparatus do not require 
such addition, because a considerable quantity of the acid in the 
clay cell gradually penetrates by osmose into the bath ; and not 
only of the acid alone, but also of the white vitriol solution 
formed, whereby the working duration of the bath is considera- 
bly reduced. Furthermore, the sulphuric acid liberated by the 
separation of copper from the blue vitriol finds no saturation ; so 
that such a bath finally contains an excess of acid which for the 
production of good deposits must from time to time be removed, 
if it is not preferred to throw the bath away and make a fresh 
one. The simplest method of removing the excess of acid is to 
add to the bath pure carbonate of copper as long as strong effer- 
vescence takes place, blue vitriol being thereby formed, and hence 
the bath at the same time strengthened. Some operators remove 
the excess of acid by adding to the bath whiting free from iron, 
until no more effervescence takes place, and then filtering off from 
the calcium sulphate (gypsum) formed. The first-mentioned pro- 
cess is, however, preferable in every respect. 

2. Galvanoplastic Deposition by the Battery and Dynamo 
Machine. 

Since it has been shown in the preceding section that a cell 
apparatus is to be considered as a Daniell element closed in itself, 
it will not be difficult to comprehend that in economical respects 
no advantage is offered by the production of galvanoplastic de- 
positions by a separate battery, because in both cases the chemical 
work is the same and the zinc dissolved by the use of Daniell or 
Bunsen elements effects no greater quantity of copper deposit in 
the bath than the same quantity of zinc dissolved in the cells of 
the single apparatus. In other respects the use of a battery, how- 
ever, offers great advantages. The employment of external 
sources of current requires the same arrangement as shown in 
Figs. 36 and 37, pp. 84 and 85 ; copper anodes being placed in 
the bath which are connected with the anode pole of the battery. 

By this arrangement, while the copper is being deposited upon 
the mould, the copper anodes become dissolved by the sulphuric 
acid set free, forming sulphate of copper, which continued action 



GALVANOPLASTY. 279 

keeps the copper content of the bath quite constant. Further- 
more, no foreign metallic admixtures reach the bath as is the case 
in the single cell apparatus by the white vitriol solution penetrating 
from the clay cell into the bath and causing the formation of rough 
and brittle deposits of copper. The principal advantage, how- 
ever, is that by placing a resistance board in the circuit, the cur- 
rent-strength can be controlled so that the deposits can be quickly 
covered with a strong current and then augumented with a weaker 
current, and that by intelligently regulating the current-strength, 
strongly depressed portions can also be covered, which is difficult 
in the single cell apparatus. 

A. Depositions with the Battery. 

The Daniell element described on p. 47, which yields a 
tension of about 1 volt, is much liked for this purpose. Since 
the copper bath for galvanoplastic purposes requires for its de- 
composition an electromotive force of only 0.5 to 1 volt, it will 
be best for slightly depressed moulds to couple the elements for 
quantity (Fig. 2, p. 32), alongside each other, and only in cases 
where the particular kind of moulds requires a current of stronger 
tension, to couple two elements for tension one after the other, an 
excess of current being rendered innoxious by means of the resist- 
ance board or by suspending larger surfaces. 

Bunsen elements may, however, be used to great advantage, 
since the zincs of the Daniell elements become tarnished with 
copper and have to be frequently cleansed if the process is not to 
be retarded or entirely interrupted. The Bunsen elements need 
only be coupled for quantity, their electromotive power being con- 
siderably greater. To be sure the running expenses are much 
greater than with Daniell elements, at least when nitric acid is 
used for filling. All that has been said under " Electro-plating 
arrangements in particular," page 79, in regard to conducting the 
current, the resistance boards, conducting rods, anodes, etc., is also 
valid for plants for the galvanoplastic deposition of copper with 
the battery. 



280 ELECTKO-DEPOSITION OF METALS. 

B. Depositions with Dynamo- Machines. 

It is best to use dynamos capable of yielding a large quantity 
of current with a tension of 2, or, at the utmost, 2J volts. In 
order to avoid repetition the reader is referred to what has been 
said under " Arrangements with dynamo-electric machines/' page 
91, the directions given there applying also to the galvanoplastic 
process. Since only in very rare cases the object-surface will be 
the same in all baths, it will be advisable to supply each of the 
baths, if several of them are worked with one dynamo-machine, 
with a resistance board and a voltmeter. 

Copper baths for galvanoplastic depositions with a separate source 
of current. — The directions for the composition of the bath vary 
very much, some authors recommending a copper solution of 18° 
Be. which is brought up to 22° Be. by the addition of pure con- 
centrated sulphuric acid. Others again increase the specific 
gravity of the bath up to 25° Be. by the addition of sulphuric 
acid, while some prescribe an addition of 5 to 7 per cent, of sul- 
phuric acid. It is difficult to give a general formula suitable for 
all cases, because the addition of sulphuric acid will vary accord- 
ing to the current-strength at disposal, the nature of the moulds 
and the distance of the anodes from the objects. The object of 
adding sulphuric acid is, on the one hand, to render the bath 
more conductive, and when used in proper proportions, to make 
the deposit more elastic and smoother, and prevent the brittleness 
and coarse-grained structure which, under certain conditions, 
appear. When depositing with a battery somewhat more sul- 
phuric acid may be added to the bath than when employing the 
current of a dynamo-electric machine. The following com- 
positions have, in most cases, been found suitable for the repro- 
duction of shallow, as well as of deep, moulds. 

I. For depositing with the dynamo. — Blue vitriol solution of 
18° Be. 100 quarts, pure sulphuric acid of 66° Be. 1 to 1 J quarts. 

II. For depositing with the battery. — Blue vitriol solution of 
18° Be. 100 quarts, pure sulphuric acid of 66° Be. 1 J to 2 quarts. 

For some special uses, the composition of the bath has to be 
somewhat modified, which will be referred to later on. In regard 
to the elasticity, strength, and hardness of galvanoplastic depositions 



GALVANOPLASTY. 



281 



of copper, v. Hiibl found that copper of great toughness, but of 
less hardness and strength, is obtained with a current-density of 
0.6-1.0 ampere from an 18 per cent, blue vitriol solution, and 
copper of great hardness and strength, but of little toughness, 
with 2 to 3 amperes, from a 20 per cent, solution. 

For copper printing plates, a 20 per cent, solution compounded 
with 3 per cent, of sulphuric acid, and a current-density of 1 .3 
amperes, were found the most suitable. 

Many operators prefer as a bath a solution of pure blue vitriol 
of 22° Be., without any addition of sulphuric acid. A good 
deposit is obtained in such a bath, but a tension of 2 to 2J 
volts is required, while acidulated baths need only f to 1J volts, 
according to the content of acid. 

Very fine deposits have also been obtained in baths consisting 
of a blue vitriol solution of 21° Be., brought up to 22° by the 
addition of sulphuric acid. This shows that it is not necessary 
to stick to a fixed unlimited composition of the baths, provided 
it is understood how to bring the current-condition into harmony 
with the composition. 

According to the composition of the bath, a fixed minimum 
and maximum current-density corresponds to it, which must not 
be exceeded if useful deposits are to be obtained. There is how- 
ever a further difference according to whether the bath is at rest 
or in motion ; v. Hiibl obtained the following results : — 





Minimum and maximum current-density 




per 15.5 square inches. 


Composition of solution. 








With solution at 


With solution in 




rest. 


gentle motion. 




Amperes. 


Amperes. 


15 per cent, blue vitriol, without sul- 






phuric acid ..... 


2.6 to 3.9 


3.9 to 5.2 


15 per cent, blue vitriol, with 6 per 






cent, sulphuric acid 


1.5 " 2.3 


2.3 " 3.0 


20 per cent, blue vitriol, without sul- 






phuric acid ..... 


3.4 " 5.1 


5.1 " 6.8 


20 per cent, blue vitriol, with 6 per 






cent, sulphuric acid 


2.0 " 3.0 


3.0 " 4.0 



Touching the addition of sulphuric acid, it was shown that no 
difference in the texture of the deposit is perceptible if the addi- 
tion of acid varies between 2 and 8 per cent. 



282 



ELECTRO-DEPOSITION OF METALS. 




The preceding table shows that 
a copper bath in gentle motion 
can stand considerably higher 
current-densities, and hence will 
work with correspondingly great- 
er activity than a bath at rest. 
In the electrolytic refining of 
copper, it was found that for 
the faultless deposition of cop- 
per, the bath must be maintained 
entirely homogeneous in all its 
parts. When a copper bath is 
at rest and the depositing opera- 
tion in progress, the upper layers 
of the bath become poorer in cop- 
per than the lower, while at the 
same time they contain more sul- 
phuric acid. This difference in 
the composition of the upper and 
lower layers has the disadvantage 
that the portions dipping into the 
layers richer in copper become 
more thickly coppered than those 
in the upper layers. Baths which 
are constantly in gentle motion 
show less inclination to the for- 
mation of knots and other rough 
excrescences, and hence the cur- 
rent-density may be greater than 
with solutions at rest resulting in 
the deposition being effected with 
greater rapidity. These experi- 
ences gathered in electro-metal- 
lurgical operations on a large 
scale, have been advantageously 
applied to galvanoplasty. The 
constant motion of the copper 
bath may be effected in various 



GALVANOPLASTY. 283 

ways. Stirring by hand is frequently relied upon, but it is 
liable to be accidentally omitted, and being of necessity inter- 
mittent allows time for partial separation to occur between two 
consecutive stirrings. Mechanical agitation, which is more cer- 
tain in its effects, may be applied by working a small screw pro- 
peller slowly at one end of the bath or by blowing air into the 
solution constantly through a tube passing to the bottom of the 
vat, by means of a fan-blower or other arrangement. 

Where many copper baths are in operation, the agitation of 
the bath may be effected as follows : The baths are arranged in 
the form of steps ; near the bottom each bath is provided with a 
leaden outlet-pipe (Fig. 92), which terminates over the next bath 
over a distributing gutter, or as a perforated pipe, h. From the 
last bath the copper solution flows into a reservoir, E, from which 
it is forced by means of a hard-rubber pump, i, into the reservoir 
A, placed at a higher level ; from A it again passes through the 
baths B, 0, and I). A leaden steam coil may, if necessary, be 
placed in A, to increase the temperature if it should have become 
too low. Over A a wooden frame covered with felt may be 
placed ; the copper solution flowing upon the frame and passing 
through the felt is thereby filtered. 

Whatever motion is given to the bath it must be sufficiently 
vigorous to insure thorough mixture of the solution, but without 
disturbing the relative positions of anode and cathode, and the 
mechanism must be so applied that it in no way lessens the facili- 
ties for examining the progress of deposition. 

Annealed sheets of pure copper are used as anodes ; impure 
anodes introduce other metallic constituents into the bath, which 
might result in a brittle deposit. It is recommended daily to free 
the anodes from adhering residues by brushing so as to decrease 
the collection of slime in the bath. 

The anodes should present at least as large a surface as the 
cathodes ; for flat moulds the distance between them and the 
anodes may be two to three inches, but has to be increased for 
deeper moulds. The copper withdrawn from the bath by depo- 
sition being only partially replaced by the anodes, the content of 
free acid will increase in consequence of the reduction of the con- 
tent of copper. However, the copper wanting can be readily 



284 ELECTRO-DEPOSITION OF METALS. 

replaced by suspending bags filled with blue vitriol in the bath, 
while too large an excess of acid is removed by the addition of 
copper carbonate. 

Determination of free acid. — The free acid is determined by 
titrating the copper solution with normal soda solution, congo 
paper being used as an indicator. Bring by means of a pipette, 
10 cubic centimetres of the copper bath into a beaker glass, dilute 
with the same quantity of distilled water, and add drop by drop 
from a burette normal soda solution, stirring constantly, until 
congo paper is no longer colored blue, when moistened with a drop 
of the solution in the beaker glass. The cubic centimetres of 
normal soda solution consumed multiplied by 4.9 give the num- 
ber of grammes of sulphuric acid in the liter. 

Suppose up to the appearance of the final reaction by means of 
congo paper, which indicates that all the free sulphuric acid has 
been saturated by the normal soda solution, 11.99 cubic centi- 
metres of normal soda solution had been used for 10 cubic 
centimetres of copper bath, then one liter of the bath contains 
11.9 X 4.9 = 58.31 grammes of sulphuric acid. 

Determination of the content of copper according to Haen. — This 
method is based upon the conversion of blue vitriol and potassium 
iodide into copper iodide and free iodine. By determining the 
quantity of separated free iodine by titrating with solution of 
sodium hyposulphite of known content, the content of blue vitriol 
is found by simple calculation. The process is as follows : 
Bring 10 cubic centimetres of the copper bath into a measuring 
flask holding ^ liter, neutralize the free acid by the addition of 
dilute soda lye until a precipitate of bluish cupric hydrate, which 
does not disappear even with vigorous shaking, commences to 
separate. Now add, drop by drop, dilute sulphuric acid until 
the precipitate just dissolves ; then fill the measuring flask up to 
the mark with distilled water, and mix by vigorous shaking. Of 
this solution bring 10 cubic centimetres by means of a pipette 
into a flask of 100 cubic centimetres 7 capacity and provided with 
a glass stopper; add 10 cubic centimetres of a 10 per cent, 
potassium iodide solution, dilute with some water, and allow the 
closed vessel to stand about 10 minutes. Now add from a burette, 
with constant stirring, a deci normal solution of sodium hyposul- 



GALVANOPLASTY. 285 

phite until starch-paper is no longer colored blue by a drop of 
the solution in the flask. Since 1 cubic centimetre of decinormal 
solution corresponds to 0.0249 gramme of blue vitriol (= 0.0063 
gramme of copper) the content of blue vitriol in one liter of the 
solution is found by multiplying the number of cubic centimetres 
of decinormal solution consumed by 24.9. For the correctness 
of the result it is necessary that the copper bath should be free 
from iron. 

Suppose 7.2 cubic centimetres of decinormal solution of sodium 
hyposulphite have been used, the bath would contain 7.2 x 24.9 
= 179.28 grammes of blue vitriol. 

If now by these two determinations, the content of free acid 
and of blue vitriol in the bath has been ascertained, a comparison 
with the contents originally present in preparing the bath will 
show how many grammes per liter the content of acid has in- 
creased, and how many grammes the content of copper has de- 
creased. Then by a simple calculation it is found how much dry 
pure carbonate of copper has to be added per liter of solution to 
restore the original composition. For each gramme more of sul- 
phuric acid than originally present, 1.26 grammes of carbonate 
of copper have to be added, and each gramme of carbonate of 
copper increases the content of blue vitriol 2.02 grammes per liter 
of bath. By reference to these data the operator is enabled to 
calculate whether the quantity of carbonate of copper added for 
the neutralization of the excess of free acid suffices to restore the 
original content of blue vitriol ; or whether, and how much, blue 
vitriol per liter has to be added. 

Preparation of moulds (matrices) in plastic material. — If a nega- 
tive of the original for the production of copies is not to be made 
by direct deposition upon a metallic object, the negative has to be 
prepared by moulding the original in a plastic mass which on 
hardening will retain the forms and lines of the design to the 
finest hatchings. Gutta percha, wax (stearine, etc.), plaster of 
Paris, glue, and a few readily fusible metals are suitable materials 
for this purpose. 

Since the galvanoplastic process as far as it applies to electro- 
typing, will next be considered, we first direct our attention to the 
preparation of moulds or matrices of gutta-percha and wax, the 



286 ELECTRO-DEPOSITION OF METALS. 

only materials suitable for this purpose, and which are generally 
used. 

1. Moulding in gutta-percha. — For the reproduction of the 
fine lines of a wood-cut or copper plate, pure gutta-percha freed 
by various cleansing processes from the woody fibres, earthy 
substances, etc., found in the crude product, is very suitable. 
Besides the requisite degree of purity, the gutta-percha should 
possess three other properties, viz., it must become highly plastic 
by heating, without, however, becoming sticky, and finally it 
should rapidly harden. 

The most simple way of softening gutta-percha is to place it in 
water of 176° to 194° F. When thoroughly softened no hard 
lumps should be felt in kneading with the hands, in doing which 
the latter should be kept thoroughly moistened with water. A 
fragment corresponding to the size of the object to be moulded is 
then rolled into a plate about J to j inch thick. To facilitate 
the detachment of the mould after cooling, the surfaces of the 
objects to be moulded, as well as the side of the gutta-percha 
which is to receive the impression, should be well brushed with 
black-lead (plumbago or graphite). The black-leaded surfaces 
are then placed one upon the other, and after gently pressing the 
gutta-percha with the hand upon the original the whole is placed 
in the press. To stop the further movement of the press-plate 
and prevent injury to the mould by too strong a pressure, small 
iron blocks, somewhat higher than the frame containing the object 
to be moulded and the gutta-percha plate, are placed on both sides 
of the frame. The screw of the press is then made to act until 
the press-plate touches the iron blocks ; under this pressure the 
gutta-percha is allowed to cool and harden. 

For making the impression of the form in the moulding com- 
position, a moulding press is used which is capable of giving a 
gradual and powerful pressure. Fig. 93 represents a form of 
moulding press in common use, and known as the "toggle" 
press. It consists of a massive frame having a planed movable 
bed over which a head is swung on pivots and counter-balanced 
by a heavy weight, as shown, so that it can be readily thrown up, 
leaving the bed exposed, the black-leaded type-form being placed 
on the bed. The well black-leaded case is attached by clamps to 



GALVANOPLASTY. 



287 



the movable head, or the form (also black-leaded) is laid face 
down on the case, and the head is then turned down and held in 



Fig. 93. 




place by the swinging bar (shown turned back in the cut). All 
being ready, the toggle-pressure is put on by means of the hand- 
wheel and screw, the result being to raise the bed of the press 
with an enormous pressure, causing the face of the type-form to 
impress itself into the exposed moulding surface. 

Fig. 94 represents a form of " hydraulic" press less commonly 
used than that just described. It is provided with projecting 
rails and sliding plate, on which the form and case are arranged 
before being placed in the press. The pump which is worked by 



288 ELECTRO-DEPOSITION OF METALS. 

hand is supported by a frame-work on the cistern below the 
cylinder, and is furnished with a graduated adjustable safety-valve 
to give any desired pressure. 

FiG. 94. 




2. Moulding in wax (stearine). — Beeswax is a very useful mate- 
rial for preparing moulds, but, like stearine, it is according to the 
temperature now softer and now harder, which must be taken 
into consideration. In the cold, pure beeswax is quite brittle and 
apt to become full of fissures in pressing. To decrease the brittle- 
ness certain additions are made to the wax, Urquart recommend- 
ing the following mixture which is frequently used in England : 
Beeswax 85 parts by weight, Venice turpentine 13, black-lead 
finely pulverized 2. 

According to Volkmer a good mixture is obtained by melting 
together 70 parts of wax and 30 of stearine. Watt prefers a 
mixture consisting of 70 parts of wax, 26 of stearine, and 4 of 
litharge or flake-white. G. L. v. Kress recommends the follow- 
ing mixture: White wax 42.32 ozs., stearine 14.11 to 21.16 ozs v 



GALVANOPLASTY. 289 

tallow 10.58 ozs., graphite 1.76 ozs. First melt the asphalt over 
a moderate fire, then add the wax, stearine, and tallow, and when 
these are melted, the graphite ; stir until the mixture begins to 
congeal. 

To prepare the wax mould pour the melted composition into 
flat metallic trays provided w r ith loops for suspension in the bath. 
When the composition is nearly set remove any bubbles of air or 
impurities from the surface with blotting paper. After black- 
leading the surface press the original, also black-leaded, upon the 
composition and submit the whole to pressure until cold. When 
the black-leading has been carefully done there is no difficulty in 
detaching the original after cooling ; many operators slightly oil 
the surface of the original instead of black-leading. 

When the mould of gutta-percha or wax has been properly 
made, it is thoroughly black-leaded in order to give it a conduct- 
ing surface upon w T hich the galvanic deposition of the copper may 
take place. Black-leading must be very thorough so that the 
black-lead penetrates into every line and letter of the mould, 
otherwise the copper deposited on the surface will be an imperfect 
copy of the original, and it will be useless to place the mould in 
the bath. The black-lead used in every stage of the electrotyping 
process must be of the purest description and in the most minute 
state of division. The best material for the purpose is prepared 
from the purest selected Ceylon graphite, which is ground by 
rolling with heavy iron balls until it is reduced to a dead-black, 
impalpable powder. 

Black-leading the moulds is performed either by hand or more 
commonly by machines. 

Fig. 95 shows one of these machines with its cover removed to 
exhibit its construction. It has a travelling carriage holding one 
or more forms, which passes backward and forward, under a later- 
ally vibrating brush. Beneath the machine is placed an apron 
which catches the powder which is again used. 

Another construction of a black -leading machine is shown in 
Fig. 96, the details of which will be understood without lengthy 
description. The moulds are placed upon the slowly revolving, 
horizontal wheel upon which the brush moves rapidly up and 
down with a vertical, and at the same time laterally, vibrating 

19 



290 



ELECTRO-DEPOSITION OF METALS. 



motion. The black-leading space being closed air-tight, scatter- 
ing of black-lead dust is entirely prevented, the excess of black- 
lead collecting in a vessel placed in the pedestal. 

Fig. 95. 




On account of the dirt and dust caused by the dry process of 
black-leading, some electrotypers prefer the wet process invented 
by Mr. Silas P. Knight, of New York. This process is designed 
to work more quickly and neatly, producing moulds that are 
thinly, evenly, and perfectly covered. The moulds are placed upon 
a shelf in a suitable receptacle, and a rotary pump forces an emul- 
sion of graphite and water over their surfaces through a travelling 
fine-rose nozzle. This process is pronounced to be rapid, efficient, 
neat, and economical. 



GALVANOPLASTY. 



291 



With very deep forms of type, it is sometimes of advantage to 
first coat the black-leaded surface with copper, in order to obtain 




a uniform deposit in the bath. The process is as follows : Pour 
alcohol over the black-leaded form, let it run off and then place 
the form horizontally over a water trough. Now pour over the 
form blue vitriol solution of 15° to 16° Be., dust upon it from a 
pepper-box some impalpably fine iron filings and brush the mix- 
ture over the whole surface, which thus becomes coated with a 
thin, bright, adherent film of copper. Should any portion of the 
surface after such treatment remain uncoppered, the operation is 
repeated. The excess of copper is washed off and the form, after 
being provided with the necessary conducting wires, is ready for 
the bath. 

Gilt and silvered black-lead is also sometimes used for very 
deep forms. It is, however, cheaper to mix the black-lead with 
J its weight of finest white bronze powder from finely divided 
tin. When forms thus black-leaded are brought into the copper 



292 ELECTRO-DEPOSITION OF METAES. 

bath, the particles of tin become coated with copper, also causing 
a deposit upon the black-lead particles in contact with them. 

After black-leading the workman takes one or several stout 
copper wires, the ends of which, after thorough cleansing, he 
heats for an instant, and imbeds them in the wax on the side of the 
mould. The surface of this wire is carefully exposed, and by 
way of precaution, the place is rubbed with black-lead with the 
linger to restore the black-lead surface that may have been 
disturbed. Trifling as this circumstance of exposing the imbedded 
wire may appear, the galvanic deposit of the copper on the face 
of the mould would be impossible were it neglected, as the mass 
of wax being a non-conductor of electricity, a galvanic current 
could not otherwise be established. The exposure of the wire, 
therefore, is essential in order that the surface of the mould may 
be rendered properly conductive to insure the uniform deposition 
of copper upon it. To confine the deposit of copper where it is 
actually desired, and to prevent it from unnecessarily spreading 
over the edges of the mould, a tool called the " building iron" is 
heated and run over the mould so as to destroy the continuity of 
the black-lead surface, save where the deposit of copper is 
wanted. 

In order that the deposition of copper may be as nearly uniform 
in thickness as possible over the entire surface of the mould, it 
becomes necessary, where a large surface is to be coated, to pro- 
vide as much metallic surface as possible on which the deposit of 
copper may commence and spread. One method of accomplishing 
this, is to attach one or more pieces of metal to the wax on the 
edges of the mould, and connect them with the slinging wires by 
good metallic connections. 

A very practical device in this connection is the " electric-con- 
nection gripper" of Messrs. E. Hoe & Co. of New York. This 
arrangement is designed to hold and sustain the moulding case, 
and at the same time to make an electric connection with the pre- 
pared conducting face of the mould only ; consequently, leaving 
the metal case itself entirely out of the current, so that no copper 
can be deposited on it. 

Gutta-percha being specifically lighter than water, moulds of 
this material have to be provided with a piece of heated lead stuck 



GALVANOPLASTY. 293 

to the back to prevent them from floating, and to force them to 
occupy a perpendicular position opposite to the anodes. 

The moulds are suspended in the bath in the same manner as 
in other galvanic processes, special care being had that their sur- 
faces hang parallel to the anodes, so that all portions may receive 
a uniform deposit. Before placing the mould in the bath, pour 
over it, while in a horizontal position, a mixture of equal parts 
of alcohol and water ; by this means, a uniform moistening of the 
mould in the bath is attained, and the settlement of air-bubbles 
on it prevented. 

For the production of a dense, coherent, and elastic deposit in 
the acid-copper bath, the chief requisite is to have the current- 
strength in the correct proportion to the surface to be coated, this 
applying to deposition with the single-cell apparatus, as well as 
with an external source of current. 

The stronger the sulphuric acid in the clay cells of the simple 
apparatus is, with the greater rapidity it acts upon the zinc plates, 
and the more quickly is the copper deposited upon the moulds. If 
the zinc surface of the clay cells is very large in proportion to the 
surface of the moulds, the deposition of copper also takes place 
with correspondingly greater rapidity. However, a rapid depo- 
sition of copper is to be avoided, if deposits possessing the above- 
mentioned desirable properties are to be obtained, because a deposit 
forced too much, turns out incoherent, lacking in density, is fre- 
quently blistered, and, with too strong action, is even pulverulent. 
The color of the deposit furnishes a certain criterion for its 
quality ; a red-brown color indicating an unsuitable deposit, and 
a beautiful rose color a good serviceable one. 

One part of concentrated sulphuric acid of 66° Be. to 30 
of water has formerly been given as the proper proportions 
for the dilute acid used for filling the clay cells, provided the 
zinc surface be about the same as that of the moulds. If the 
zinc surface is smaller than that of the moulds, stronger acid may 
be used, but if it is larger, the acid will have to be more dilute. 
The correct concentration of the acid in the clay cells may be 
readily determined by the progressive result of the deposit and 
its color. Deep moulds require a stronger current, and hence 
acid of greater strength than flat moulds ; however, if after such 



294 ELECTRO-DEPOSITION OF METALS. 

deep moulds are provided with a preliminary deposit, the current 
proves too strong for the correct progress of the operation, its 
action may be weakened by either diluting the acid in the clay 
cells with water, or by taking out a few zinc plates, or by hang- 
ing a few copper sheets upon the object-rods, or suspending more 
moulds. 

For the deposition of copper with a separate source of current 
(battery or dynamo), the same that has been said above applies as 
regards the current-strength, which must be brought to a suitable 
degree by the resistance board. The most suitable current-density 
for the production of a good deposit is 1.5 to 2 amperes per 15J 
square inches of surface of moulds for baths of the composition 
given on page 280, if at rest, and 2 to 3 amperes, if in motion. 

Since even for deeper moulds a tension of 1.5 volts suffices, if 
the bath is acidulated, the more powerful Bunsen elements will 
have to be coupled alongside one another ; but two of the weaker 
Daniell or Lallande elements one after the other, and of such 
groups, as many as are required, will have to be coupled along- 
side one another for quantity of current (see page 32), to make 
the active zinc surface nearly equal to that of the moulds. How- 
ever, for flat moulds coupling the separate weaker elements along- 
side one another is also sufficient. When the moulds are coated 
with copper on every side, and also the deeper portions, the cur- 
rent is weakened if a copper deposit of pulverulent or coarse- 
grained structure and of a dark color should appear on the edges 
of the moulds, and it is feared that the deposit upon the design 
or type might also turn out pulverulent. The current, however, 
should only be sufficiently weakened to prevent a further pro- 
gress of the dark deposit on the edges towards the interior of the 
surface of the mould. If, however, by too strong a current the 
separation of a pulverulent deposit upon the design has already 
taken place, the deposit may generally be saved, if the fact is 
noticed in time, and the current correspondingly weakened, as the 
layers are firmly united by the coherent copper then deposited. 

The current of the dynamo machine must also be sufficiently 
weakened by the resistance board in front of the bath, or by that 
of the machine to guarantee the good quality of the deposit. For 
deeper moulds the tension for covering may amount to 1 or 1.5 



GALVANOPLASTY. 295 

volts, and for very deep arid steep moulds to 1.5 or 2 volts. But 
when the moulds are completely covered the current is reduced to 
about 0.75 volt,* and the operation finished with this tension. 

The average time required for the production of a sufficiently 
heavy deposit with a dynamo machine is from 7 to 8 hours. In 
this time the deposit acquires a thickness of about ^ millimetre 
(0.013 inch) which corresponds to a weight of about 25 grammes 
(14.11 drachms) of copper per 15J square inches; 

Now, since it frequently happens that an electrotype has to be 
finished and delivered in a hurry, the work may have to be con- 
tinued during the night ; but as it may not be desirable to have 
the dynamo running, either a cell apparatus or accumulators have 
to be employed. In using a cell apparatus, it is advisable to first 
quickly coat the moulds with the current of the dynamo, and then 
finish the deposit in the apparatus. 

In modern times accumulators have been successfully used for 
the same purpose. 

A detailed description of the accumulators and directions for 
their treatment may here be omitted, they being furnished by the 
manufacturers of the various systems. Each accumulator con- 
sists of a number of alternately positive and negative lead plates 
immersed in a vessel filled with dilute sulphuric acid. By con- 
ducting the current of a dynamo machine into the accumulator 
so that the positive current passes into the positive plates, and the 
negative current into the negative plates, lead peroxide is formed 
upon and in the porous positive plates by the co-operation of the 
sulphuric acid and the oxygen appearing on the positive pole, and 
the greater the quantity of lead peroxide thus formed, the more 
electricity is stored in the accumulators. These operations are 
called charging the accumulator. By interrupting the introduc- 
tion of current and closing the circuit of the positive and nega- 
tive plate systems by the introduction of electrodes in an electro- 
lyte (galvanic bath), a current is developed, whereby the lead 
peroxide of the positive plates which has been formed is reduced 
to lead, while the negative plates are oxidized to lead peroxide. 
This process is termed discharging. The chemical processes ap- 

* These current-strengths refer to formulae I and II given on page 280. 



296 ELECTRO-DEPOSITION OF METALS. 

pearing thereby are of a more complicated nature than here given, 
but are omitted so as to render, comprehension of the process 
less difficult. The directions for charging and discharging the 
accumulator must be strictly followed, and require great atten- 
tion, as charging with too strong a current, or a too abundant 
discharge may cause the rapid destruction of the plates. The 
charging is best done during the day with a special small dynamo- 
machine. 

Detaching the deposit from the mould. — When the mould has 
received a suitable deposit, it is taken from the bath, rinsed in 
water and all edges which might obstruct the detachment of the 
deposit from the mould are removed with a knife. From gutta- 
percha moulds the deposit is gradually lifted by inserting under 
one corner a flat horn plate or a thin dull brass blade and apply- 
ing a very moderate pressure ; particles of gutta-percha which 
may remain adhering are carefully burnt off over a flame. Wax 
moulds are placed in an inclined position, and a stream of hot 
water is poured over the copper surface, by which means the wax 
is sufficiently softened to allow the shell of copper to be stripped 
off. This may be done by taking hold of one corner of the shell 
and quickly lifting it as the hot water flows over it. In removing 
the shell care should be taken to keep it straight, as otherwise it 
will be difficult to back and finish it properly. 

Backing the deposit or shell. — The tinning of the back of the 
shell is the next operation, and has for its object to strengthen the 
union between the shell and the backing metal. For this purpose 
the back of the shell is cleansed by brushing with "soldering fluid," 
made by allowing muriatic acid to take up as much zinc as it will 
dissolve, and diluting with about J of water, to which some sal 
ammoniac is sometimes added. Then the shell, face down, is 
heated by laying it upon an iron soldering plate, floated on a bath 
of melted stereotype metal, and, when hot enough, melted solder 
(half lead and half tin), is poured over the back, which gives it 
a clean, bright metallic covering. Or, the shell is placed down- 
ward in the backing pan, brushed over the back with the solder- 
ing fluid, alloyed tinfoil spread over it, and the pan floated on the 
hot backing metal until the foil melts and completely covers the 
shell. When the foil is melted the backing pan is swung on to a 



GALVANOPLASTY. 



297 



levelling stand, and the melted backing metal is carefully poured 
on the back of the shell from an iron ladle, commencing at one 
of the corners, and gradually running over the surface until it is 
covered with a backing of sufficient thickness. Another method 
is as follows : After tinning the shell it is allowed to take the 
temperature of the backing metal on the floating iron plate. The 
plate is then removed from the melted metal, supported in a level 
position on a table having projecting iron pins on which it is 
rested, and the melted stereotype metal is carefully ladled to the 
proper thickness on the back of the tinned shell. This process is 
called " backing." The thickness of the metal-backing is about 
an eighth of an inch. A good composition for backing metal 
consists of lead 90 parts, tin 5, and antimony 5. 

Fig. 97. 




Finishing. — For this purpose the plates go first to the saw table 
(Fig. 97), for the removal of the rough edges by means of a 
circular saw. The plates are then shaved to take off auy rough- 



298 



ELECTRO-DEPOSITION OF METALS. 



ness from the back and make them of even thickness. In large 
establishments this portion of the work, which is very laborious, 
is done with a power planing or shaving machine, types of which 
are shown in Figs. 98 and 99, Fig. 98 being a shaving machine 

Fig. 98. 




with steam one way, and Fig. 99 one with steam both ways. 
The flatness of the plates is then tested with a straight edge and 
any unevenness rectified by gentle blows with a polished hammer, 
taking every care that the face be not damaged. The plate then 
passes to the hand shaving machine, where the back is shaved 
down to the proper thickness, smooth and level. The edges of 
the plate are then planed down square and to a proper size, and 
finally the plates are mounted on wood type-high. Book-work 
is generally not mounted on wood, the plates being left un- 



GALVANOPLASTY. 



299 



mounted and finished with bevelled edges, by which they are 
secured on suitable plate-blocks of wood or iron supplied with 
gripping pieces, which hold them firmly at the proper height and 
enable them to be properly locked up. 



Fig. 99. 




Finally, it remains to say a few words about the process by 
which a copy may be directly made from a metallic surface with- 
out the interposition of wax or gutta-percha. If the metallic 
surface to be moulded is free from grease and oxide, the deposit 
would adhere so firmly as to render its separation without injury 
almost impossible. Hence, the metallic original must first un- 
dergo special preparation, so as to bring it into a condition favor- 
able to the detachment of the deposit. This is done by thoroughly 
rubbing the original with an oily rag or, still better, by lightly 
silvering it and exposing the silvering for a few minutes to an 
atmosphere of sulphuretted hydrogen, whereby sulphide of silver 
is formed, which is a good conductor, but prevents the adherence 
of the deposit to the original. For the purpose of silvering, free 
the surface of the metallic original (of brass, copper or bronze) 



300 ELECTRO-DEPOSITION OF METALS. 

from grease, and pickle it by washing with dilute potassium 
cyanide solution (1 part potassium cyanide to 20 water.) Then 
brush it over with a solution of 4J drachms of nitrate of silver 
and 1 oz. 6 drachms of potassium cyanide (98 per cent.) in 1 
quart of water; or, still better, immerse the original for a few 
seconds in this bath, until the surface is uniformly coated with 
a film of silver. The production of the layer of sulphide of 
silver is effected according to the process described later on 
(p. 307). The negative thus obtained is also silvered, made 
yellow with sulphuretted hydrogen, and a deposit of copper is 
then made, which represents an exact copy of the original. In- 
stead of sulphurizing the silvering with sulphuretted hydrogen, 
it may also be iodized by washing with dilute solution of iodine 
in alcohol. The washed plate, prior to bringing it into the copper 
bath, is for some time exposed to the light. 

To prevent the separation of copper on the back of the metallic 
original to be copied, it is coated with asphalt lacquer, which must 
be thoroughly dry before bringing into the bath. When the de- 
posit of copper is of sufficient thickness, the plate is taken from 
the bath, rinsed in water, and dried. The edges are then trimmed 
off by filing or cutting to facilitate the separation of the shell 
from the original. 

Of course, only metals which are not attacked by the acid cop- 
per solution can be directly brought into the bath. Steel plates 
must therefore first be thickly coppered in an alkaline copper 
bath (p. 183), and even this precaution does not always protect 
the plate from corrosion. It is therefore better to produce in a 
silver bath (formula I, p. 201), a copy in silver of sufficient 
thickness to allow of the separation of both plates. The silver 
plate is iodized, and from it a copy in copper is made by the gal- 
vanoplastic process. The copper plate thus obtained is an exact 
copy of the original, and after previous silvering, the desired 
number of copies may be made from it. 

Electro-etching. — The plate of steel, copper or zinc is coated 
with an etching-ground, which is not attacked by the bath, and 
the design traced with a graver, taking care that the tool lays 
bare the metal in all the lines. By using the plate thus prepared 
as the anode, and suspending another plate of the same size at 



GALVANOPLASTY. 301 

the negative pole, the latter will receive the deposit, while the 
former will be eaten away at the places uncovered by the graver. 
For copper plates which are to be etched, the ordinary acid copper 
bath is used ; for zinc plates, solution of w T hite vitriol, and for 
steel plates, solution of green vitriol or of ammonium chloride ; 
instead of baths of metallic salts, pure water slightly acidulated 
with sulphuric, muriatic or nitric acid may be used. 

For the etching-ground a melted composition of asphalt 2J parts, 
wax 2, rosin 1, and black pitch 2, serves. However, the fol- 
lowing varnish, which resists 25 per cent, nitric acid, is to be 
preferred. It is prepared as follows : Melt yellow wax 4 parts, 
Syrian asphalt 4, black pitch 1, and white Burgundy pitch 1, and 
while boiling, gradually add, with constant stirring, 4 parts more 
of pulverized Syrian asphalt. Continue the bcfiling until a sample 
poured upon a stone and allowed to cool, breaks in bending. 
Then pour the fluid mixture into cold water and shape it into small 
balls, which for use are dissolved in oil of turpentine. 

Since the current-strength is under perfect control, the etching 
may be carried to any depth desired. Some portions may be less 
etched than others by taking the plate from the bath, and after 
washing and drying, coating the portions which are not to be 
further etched with lacquer, and returning the plate to the bath. 

Printing plates in relief may in this manner be prepared by 
slightly etching the bared design of a copper-plate in the gal- 
vanoplastic copper bath, and then bringing the plate as object in 
contact with the negative pole, while a plate of chemically pure 
copper serves as anode. The deposited copper unites firmly with 
the rough copper of the etched plates, and after removing the 
etching-ground with benzine or oil of turpentine, the design 
appears in relief. 

Heliography. — By this term are understood several methods of 
printing, in which plates of asphalt, chrome-gelatine, etc., pro- 
duced by exposure to light, are used. For our purposes only, 
the method is of interest, by which from the negative, produced 
by the action of light, a galvanoplastic reproduction — printing 
plates in high and low relief — in metal is made. The heliographic 
process invented by Pretsch, and improved by Scamoni, consists 
in taking by photography a good negative of the engraving or 



302 ELECTRO-DEPOSITION OF METALS. 

other object to be reproduced, developing with green vitriol, rein- 
forcing with pyrogallic acid and silver solution, and then fixing 
with sodium hyposulphite solution in the same manner as custo- 
mary for photographic negatives. A further reinforcement with 
chloride of mercury solution then takes place until the layer ap- 
pears light gray. Now wash thoroughly, and intensely blacken 
the light portions by pouring upon them dilute potassium cyanide 
solution. As in the photographic process, the solutions must be 
applied in abundance and without stopping, as otherwise streaks 
and stains are formed. After washing, the plate is dried, further 
reinforced, and finally coated with colorless negative varnish. 
From this negative a positive collodion picture is taken, which 
is in the same manner developed, reinforced, and fixed, the rein- 
forcement with pyrogallic acid being continued until the picture 
is quite perceptibly raised. After careful washing, pour upon the 
plate quite concentrated chloride of mercury solution, which has 
to be frequently renewed, until the picture, at first deep black, ac- 
quires a nearly white color, and the lines are perceptibly strength- 
ened. Now wash with distilled water, next with dilute potas- 
sium iodide solution, and finally with ammoniacal water, whereby 
the picture acquires first a greenish, then a brown, and finally a 
violet-brown color. After draining, the plate may progressively 
be treated with solutions of platinum chloride, gold chloride, 
green vitriol, and pyrogallic acid, the latter exerting a solidify- 
ing effect upon the pulverulent metallic deposits. The metallic 
relief is now ready ; the layer is slowly dried over alcohol, and 
the plate, when nearly cold, quickly coated with a thin rosin 
varnish, which after momentary drying, remains sufficiently 
sticky to retain a thin layer of black lead, which is applied with 
a tuft of cotton. The edge of the plate is finally surrounded with 
wax, and after being wired, the plate is brought into the galvano- 
plastic copper bath to be reproduced. 

Galvanoplastic reproduction of busts, vases, etc. — For this pur- 
pose an entirely different process of preparing the moulds than that 
described for electrotyping is required, the material for moulding 
depending on the nature of the original. Besides gutta-percha 
and wax, readily fusible metals, plaster of Paris, and glue will 
have to be considered. If the original bears heating to about 



GALVANOPLASTY. 303 

230° F., a copy in one of the readily fusible alloys given later 
on, may be made ; if it will stand heat and pressure, it is best to 
mould in gutta-percha ; but if neither heat nor pressure can be 
applied, the moulds will have to be executed in plaster of Paris 
or in glue. The manner of moulding and the material to be 
chosen furthermore depend on whether surfaces in high relief or 
round plastic bodies are to be copied, whether projecting portions 
are undercut, and whether the mould can be directly detached, or, 
if this is not the case, whether the original has to be dissected 
and moulded in separate parts. 

Regarding the practice of moulding, the reader is referred to 
special works on that subject ; only the main points for the most 
frequently occurring reproductions will here be given. 

Surfaces in relief and not undercut are readily moulded in an 
elastic mass such as gutta-percha or wax ; however, undercut 
reliefs and especially round plastic objects mostly require a plaster- 
of-Paris mould and are generally dissected ; the dissection being 
of course not carried further than absolutely necessary, because 
the separate parts must be united by a soldering seam which re- 
quires careful work, and the seam itself must be worked over and 
made invisible. Hence the section should as much as possible be 
made through smooth surfaces, edges, etc., where the subsequent 
union by a soldering seam will prove least troublesome, while 
cutting through ornaments or through portions the accurate repro- 
duction of which is of the utmost importance, should be avoided. 
Heads and busts are always executed in a core mould and in 
portions unless the entire figure is to be deposited in one piece in 
a closed mould. The section is made either through the centre 
line of the head through the nose, which, however, makes the 
subsequent union very troublesome, if the copy is to be an exact 
reproduction of the original, or the mould is divided from ear to 
ear which has the disadvantage that the deepest part of the mould 
corresponding to the nose receives the thinnest deposit. It has, 
therefore, been proposed to make two cuts so that three portions 
are formed ; one cut from one ear at the commencement of the 
growth of hair to the other ear ; and the second cut from one ear 
in a downward direction below the lower jaw in the joint of the 
head and neck, through this joint below the chin, and then up- 



304 ELECTRO-DEPOSITION OF METALS. 

wards to the other ear, and in front of it to where the hair begins. 
In bearded male heads the cat follows the contour of the beard 
and not the joint on the neck behind the beard. 

To mould round articles in gutta-percha, the softened gutta- 
percha is kneaded with wet hands upon the oiled original, or, in 
order to avoid that some portions receive a stronger pressure than 
others, and to insure a layer of gutta-percha of uniform thickness 
upon all portions, the moulding may also be executed in a ring or 
frame of iron or zinc under a press. For the rest, all that has 
been said in regard to moulding in gutta-percha on p. 286, is also 
applicable. 

The following metallic alloys have been proposed for the prepa- 
ration of moulds : — 

I. Lead 2 parts, tin 3, bismuth 5 ; fusible at 212° F. 

II. Lead 5, tin 3, bismuth 8 ; fusible at 185° F. 

III. Lead 2, tin 2, bismuth 5, mercury 1 ; fusible at 158° F. 

IV. Lead 5, tin 3, bismuth 5, mercury 2 ; fusible at 127.5° F. 
The advantage of metallic moulds consists in that the metal is 

a good conductor of electricity in consequence of which heavy de- 
posits of greater uniformity can be produced than with non- 
metallic moulds which have been made conductive by black lead. 
Nevertheless, they are but seldom employed on account of the 
crystalline structure of the alloys and the difficulty of avoiding 
the presence of air bubbles. Bottger claims that a mixture of 
lead 8 parts, tin 3, and bismuth 8, which is fusible at 227° F., 
shows a less coarse-grained structure. 

Fusible alloys containing mercury should not be used for taking 
casts of metallic objects — iron excepted — as these will amalga- 
mate with the mercury and be injured. Moreover, copper de- 
posits obtained upon such alloys are very brittle, which is due to 
the combination of the mercury with the deposited copper. 

For moulding with metallic alloys place the oiled object at the 
bottom of a flat vessel and pour the liquid metal upon it ; or 
pour the liquid metal into a box, remove the layer of oxide with a 
piece of stout paper, and when the metal is just beginning to con- 
geal firmly press the object in it. 

Plaster of Paris is used for making casts of portions from 
originals which are so strongly undercut that a mould consisting 



GALVANOPLASTY. 305 

of one piece could not be well detached from them. For taking 
casts from metallic coins and medals or from small plaster reliefs, 
it is a very convenient material. The mode of procedure is as 
follows : After the original model, say a medal, has been thoroughly 
soaped or black-leaded, wrap round the rim a piece of sufficiently 
stout paper or a thin lead foil, and bind it in such a manner by 
means of sealing-wax that the face of the medal is at the bottom 
of the receptacle thus formed. Then place the whole to a certain 
depth in a layer of fine sand, which prevents the escape of the 
semi-fluid plaster of Paris between the rim of the medal and the 
paper. Now mix plaster of Paris with water to a thin paste, 
take up a small quantity o/ this paste with a pencil or brush and 
spread it in a thin film carefully and smoothly over the face of 
the medal, then pour on the remainder of the paste up to a proper 
height and allow it to set. After a few minutes the plaster heats 
and solidifies. Then remove the surrounding paper, scrape off 
with a knife what has run between the paper and the rim of the 
medal, and carefully separate the plaster cast from the model. If 
instead of applying the first layer with a brush, the whole of the 
plaster were run at once into the receptacle, there would be great 
risk of imprisoning air bubbles between the model and the mould, 
which would consequently be worthless. The mould is finally 
made impervious and conductive according to one of the methods 
to be described later on. 

The moulding in plaster of Paris in portions, when casts from 
large plastic objects with undercut surfaces and reliefs are to be 
taken, is troublesome work, because each separate mould must not 
only be so that it can be readily separated without injury to the 
original, but must also fit closely to its neighbors. Hence thought 
and judgment are required to see of which parts separate moulds 
are to be made, or, in other words, in how many parts the mould 
is to be made. After determining on the plan of the work, the 
mode of procedure is as follows : Oil a portion of the object, if it 
consists of metal, or soap it, if of plaster of Paris, marble, wood, 
etc., and apply by means of a brush a thinly-fluid paste of plaster 
of Paris, taking care that no air bubbles are formed by the strokes 
of the brush. When this thin coat is hard, continue the applica- 
tion of plaster of Paris with a horn spatula until the coat has 
20 



306 ELECTRO-DEPOSITION OF METALS. 

acquired a thickness of j to 1 inch, and allow it to harden. Then 
separate the mould, and after cutting or sawing the edges square 
and smooth, replace it upon the portion of the original model 
corresponding to it. Now oil or soap the neighboring portions of 
the model, and at the same time, the smooth edges of the first 
mould which come in contact with the mould now to be made, 
and then proceed to make the second mould in precisely the same 
manner as the first. When the second mould is hard, trim the 
edges and replace it upon the model ; the same process being con- 
tinued until the entire original model is reproduced in moulds 
well fitting together. To prevent the finished moulds from fall- 
ing off, and to retain them in a firm position upon the original 
model, they are tied with lead wire or secured with catches of 
brass wire or sheet. When the moulds of the larger portion of 
the model, for instance, one-half of a statue, are finished, the 
so-called case or shell is made, i. e., the back of all the moulds is 
coated with a layer of plaster of Paris which holds them together ; 
this case is best made not too thin in order to attain a better resist- 
ing power. 

The entire model having been cast in the manner above 
described, and the moulds provided with the case, the whole is 
completely dried in an oven. 

The next operation is to make the plaster of Paris impervious 
to fluids, as otherwise by the moulds absorbing the acid copper 
bath, copper would be deposited in the pores of the plaster and 
the moulds be spoiled, while the copy would turn out rough instead 
of having the smooth exterior of the model. To render plaster 
of Paris and other porous substances impervious, they are satu- 
rated with wax or stearine or covered with a coat of varnish, the 
latter process being generally employed for large moulds. Apply 
a coat of thick linseed oil varnish to the face of the mould, and, 
after drying, repeat the process until the mould is thought to be 
sufficiently impervious. Rendering the mould impervious with 
wax or stearine is a better and more complete method. For this 
purpose cut a groove in the rim of the mould, place in it a brass 
wire and twist the ends which must be long enough to hold the 
mould by. The mould, having been previously dried, is then 
dipped into a bath of wax or stearine kept at a temperature of 



GALVANOPLASTY. 307 

from 180° to 212° F., and a number of air bubbles will escape 
from the mould to the surface. When the production of air 
bubbles is considerably diminished, remove the mould from the 
bath, and lay it face up in a drying oven, whereby the melting 
wax in consequence of its gravity oozes down, and the face of the 
mould is freed from an excess of wax. Whenever possible, sub- 
merging the entire mould should be avoided and the operation be 
conducted as follows : Place the heated mould in a vat filled with 
melted wax or stearine so that the face does not come in contact 
with the wax, but absorbs wax by capillarity from the back. 

The moulds thus coated with varnish or saturated with wax 
are now made conductive with black-lead, the operation being the 
same as that mentioned on p. 289. For many undercut or deep 
portions, black-leading is, however, not sufficient, and recourse 
must be had to making conductive or metalliziing by the wet way. 

Metallization by the wet way. — This method consists in the de- 
position of certain metallic salts upon the moulds and their 
reduction to metal or conversion into conductive sulphur com- 
binations. The process in general use is as follows : Apply with 
a brush upon the mould a not too concentrated solution of nitrate 
of silver in a mixture of equal parts of distilled water and 90 
per cent, alcohol. When the coat is dry expose it in a closed box 
to an atmosphere of sulphuretted hydrogen ; the latter converts the 
nitrate of silver into sulphide of silver, which is a good conductor 
of the current. For the production of the sulphuretted hydrogen 
place in the box, which contains the mould to be metallized, a 
porcelain plate or dish filled with dilute sulphuric acid (1 acid to 
8 water), and add five or six pieces of iron pyrites the size of a 
hazelnut. The development of the gas begins immed iately, and the 
box should be closed with a well-fitting cover to prevent inhaling 
the poisonous gas ; if possible, the work should be done in the 
open air or under a well-drawing chimney. The formation of the 
layer of sulphide of silver requires but a few minutes, and if not 
many moulds have to be successively treated, the acid is poured 
off from the iron pyrites and clean water poured upon the latter 
so as not to cause useless development of gas. 

It has also been recommended to decompose the silver salt by 
vapors of phosphorus and to convert it into phosphide of silver, 



308 ELECTRO-DEPOSITION OF METALS. 

a solution of phosphorus in bisulphide of carbon being used for 
the purpose. The layer of silver salt is moistened with the solu- 
tion or exposed to its vapors. This method possesses, however, 
no advantage over the preceding, because on the one hand the 
phosphorous solution takes fire spontaneously, and on the other, 
the odor of the bisulphide of carbon is still more offensive than 
that of sulphuretted hydrogen. 

A somewhat modified method is given by Parkes as follows : 
Three solutions, A, B, C, are required. Solution A is prepared by 
dissolving 0.5 part of caoutchouc cut up in fine pieces in 10 parts 
of bisulphide of carbon and adding 4 parts of melted wax ; stir 
thoroughly, then add a solution of 5 parts of phosphorus in 60 
of bisulphide of carbon together with 5 of oil of turpentine and 
4 of pulverized asphalt ; then thoroughly shake this mixture, A. 
Solution B consists of 2 parts by weight of nitrate of silver in 
600 of water; and solution C of 10 parts of chloride of gold in 
600 of water. The mould to be metallized is first provided with 
wires and then brushed over with, or immersed in, solution A, 
and after draining off, dried. The dry mould is then poured over 
with the silver solution (B), and suspended free for a few minutes 
until the surface shows a dark lustre. It is then rinsed in water 
and treated in the same manner with the chloride of gold solution 
(C), whereby it acquires a yellowish tone, when, after drying, it 
is sufficiently prepared for the reception of the deposit. Care 
must be taken in preparing solution A, as the bisulphide of carbon 
containing phosphorus may readily take fire. 

Another method is as follows : Dissolve 5 parts, by weight, of 
wax in 5 of warm oil of turpentine, and add to the solution a 
mixture of 5 parts, by weight, of phosphorus, 1 of gutta-percha, 
5 of asphalt in 120 of bisulphide of carbon. When both are 
thoroughly mixed, add to the whole a solution of 4 parts, by 
weight, of gun-cotton in 60 of alcohol, and 60 of ether, and after 
thorough shaking allow to settle. The next day pour off the 
clear solution from the sediment, when the solution can at once be 
used. It is especially well adapted for coppering parts of plants, 
leaves, flowers, etc. 

Another method of metallization is as follows : Immerse the 
leaves, etc., in iodized collodion composed of 40 per cent, alcohol, 



GALVANOPLASTY. 309 

40 cubic centimetres, ether 60 cubic centimetres, potassium iodide 
1 gramme, gun-cotton 1 gramme. 

Allow the leaves, etc., to dry so that a firmly adhering layer is 
formed ; then immerse them in a solution of 10 parts, by weight, 
of nitrate of silver iu 100 of water, whereby a layer of iodide 
of silver is formed. Now expose the article thus treated for some 
time to the light, and then immerse it in the reducing fluid, con- 
sisting of water 500 parts, by weight, green vitriol 25, and acetic 
acid of 1.04, specific gravity 25. The reduction of silver now 
progresses rapidly and the articles are ready for coppering. In 
employing this process it must not be forgotten that the layer of 
collodion will not stand rough usage, and hence injury to it by 
touching with the hands, and careless placing of the conducting 
wires have to be avoided. By. operating with the necessary care, 
the results are very satisfactory and sure. Instead of the iodized 
collodion, a mixture of equal parts of white of egg and saturated 
solution of common salt may be used, the remainder of the pro- 
cess being the same as above described. 

Metallization by metallic powders. — In some cases metallization 
by metallic powders is to be preferred to black- leading or metal- 
lizing by the wet way. Metallic or bronze powders are metals in 
the state of exceedingly fine powders of which, for galvanoplastic 
purposes, pure copper and brass powders only are of interest. 
Since such metallic powders adhere badly to waxed surfaces, the 
mould must be provided with a well-drying coat of lacquer, upon 
which before it is completely dry, the powder is scattered or sifted. 
When the lacquer is hard a smooth surface is produced by going 
over the mould with a soft brush dipped in the metallic powder, 
an excess being removed by a thin jet of water. 

Lenoir' 's process — Galvanoplastic method for originals in high 
relief. — Lenoir's method for reproducing statues in a manner 
approaches in principle to that of the foundry. He begins by 
making with gutta-percha a mould in several pieces, which are 
united together so as to form a perfect hollow mould of the origi- 
nal. This having been done, cover all the parts carefully with 
black-lead. Make a skeleton with platinum wire, following the 
general outline of the model, but smaller than the mould, since 
it must be suspended in it without any point of contact. If the 



310 ELECTRO-DEPOSITION OF METALS. 

skeleton thus prepared is inclosed in the metallized gutta-percha 
mould, and the whole immersed in the galvanoplastic bath, it will 
be sufficient to connect the inner surface of the mould with the 
negative pole of the battery, and the skeleton of platinum wires 
(which should have no points of contact with the metallized sur- 
face of the mould) with the positive pole, in order to decompose 
the solution of sulphate of copper which fills the mould. When 
the metallic deposit has reached the proper thickness, the gutta- 
percha mould is removed by any convenient process, and a faith- 
ful copy of the original will be reproduced. Lead wires may be 
substituted for the expensive platinum wires. This method re- 
quires a knowledge of the moulder's art so that good results can 
only be obtained by an experienced hand. 

Gelatine moulds. — Under certain conditions the elasticity of 
gelatine allows of the possibility of its removal from undercut or 
highly-wrought portions of the model, when it re-assumes the 
shape and position it had before removal therefrom. But gela- 
tine requires that the deposit shall be made rapidly, otherwise it 
will swell, and be partially dissolved by too long an immersion 
in the copper bath. 

To make good gelatine moulds proceed as follows : Allow white 
gelatine (cabinet-maker's glue) to swell for about 24 hours in cold 
water, then drain off the water, and heat the swollen mass in a water 
bath until completely dissolved. Compound the glue solution 
with pure glycerine in the proportion of 5 to 10 cubic centimetres 
(0.24 to 0.3 cubic inches) of glycerine to 30 grammes (1.05 ozs.) 
of gelatine, which prevents the gelatine from shrinking in cool- 
ing. When somewhat cooled off, apply the gelatine to the oiled 
original, which must be surrounded with a rim of plaster of Paris 
or wax, to prevent the gelatine from running off; when cold lift 
the gelatine mould from the model. Before metallizing and sus- 
pending in the copper bath, the mould has to be prepared to resist 
the action of the latter, as otherwise it would at once swell and be 
partially dissolved before being covered with the deposit. This 
is effected by placing the mould in a highly concentrated solution 
of tannin, which possesses the property of making gelatine inso- 
luble. 

Brandley gives the following directions for preparing gelatine 



GALVANOPLASTY. 311 

solution with an addition of tannin, which renders the moulds 
impervious to water : Dissolve 20 parts of the best gelatine in 
100 of hot water, add J part of tannic acid and the same quan- 
tity of rock candy, then mix the whole thoroughly, and pour it 
upon the model. 

The same end is reached by making a mould with gelatine 
alone, then pouring an aqueous solution of 10 per cent, of bichro- 
mate of potassium upon it, and, after draining, exposing the mould 
to the action of the sun. 

Another method is as follows : Beat into a quart of distilled 
water the whites of two eggs, filter and cover with this liquid the 
entire surface of the gelatine mould. After drying, operate with 
the solution of bichromate of potassium as in the preceding. The 
solar action renders the coating impregnated with bichromate 
insoluble. 

The mould must finally be metallized and, when in the bath, 
submitted to a strong current at the beginning. When the entire 
surface is covered with the copper deposit, and when swelling is 
no longer to be feared, a weaker current may be used. 

In the following a few special uses of galvanoplasty will be 
briefly described : — 

Nature printing, so named by Mr. v. Auer, Director of the 
Imperial Printing Office at Vienna, has for its object the galvano- 
plastic reproduction of leaves and other similar bodies. The leaf 
is placed between two plates, one of polished steel, the other of 
soft lead, and is then passed between rollers, which exert a con- 
siderable pressure. The leaf thus imparts an exact impression 
of itself and of all its veins and markings to the lead, and this 
impression may be electrotyped, and the copper plate produced 
used for printing in the ordinary way. Instead of taking the 
impression in lead, it is advisable to use gutta-percha or wax for 
delicate objects, which should previously be black-leaded or oiled. 
In the same manner galvanoplastic copies of laces, etc., may be 
obtained. 

The process used by Philipp for coating laces and tissues with 
copper and then silvering or gilding, belongs rather to electro- 
plating than to galvanoplasty. The tissue is saturated with 
melted wax, and after removing the excess with blotting paper, 



312 ELECTRO-DEPOSITION OF METALS. 

it is made conductive by black-leading with a brush. It is 
however preferable to metallize such delicate objects by the wet 
way, Parkes's method (p. 308) being especially suitable for the 
purpose, and also a treatment, with weak solution of nitrate of 
silver and pyrogallic acid frequently alternated. 

Corvin's niello. — Corvin has invented a process of producing 
inlaid work by galvanoplasty, which has been patented, and is 
now the exclusive property of J. P. Kayser & Son, of Crefeld. 
The process is as follows : A matrice of metal whose surface is 
finely polished is first made. This matrice may be used for the 
production of numerous duplicates of the same kind of object. 
The incrustations (mother-of-pearl, glass, ivory, amber, etc.) are 
then shaped by means of a saw, files, and other tools to the form 
corresponding to that which they are to occupy in the design. 
The side of the incrustations which is laid npon the matrice is, 
as a rule, smooth. The shaped incrustations, smooth side down, 
are pasted on to the parts of the model they are to occupy in the 
design. The latter being thus produced, the back of the non- 
metallic lamina is metallized, and the portions of the metallic 
plate left free are slightly oiled. By now placing the matrice 
thus prepared in the galvanoplastic bath, the copper is deposited 
not only upon the metallic matrice, but also upon the back of 
the inlaid pieces, the latter being firmly inclosed by the deposited 
metal. When the deposited metal has acquired the desired thick- 
ness, it is detached from the matrice, and incrustations with the 
right side polished are thus obtained. The lamina are more 
accurately and evenly laid in than would be possible by the 
most skilled hand- work. 

G7'asses, leaves, flowers, etc., may be coated with copper and then 
silvered, gilded or platinized, by first drying them, and after 
giving them a certain elasticity by placing in glycerine, metal- 
lizing them by Parkes's or some other method. 

Plates for the production of imitations of leather are now fre- 
quently prepared. The demand for alligator and similar leathers 
is at the present time greater than the supply, and, therefore, imi- 
tations are made by pressing ox-leather, the plates being prepared 
by galvanoplasty, as follows : A large piece of the natural skin 
or leather is made impervious to the bath by repeated coatings 



GALVANOPLASTY. 3 1 3 

with lacquer, and when completely dry, secured with asphalt 
lacquer to a copper or brass plate. The leather is then black- 
leaded and after being made conductive by copper wire or small 
lead plates, brought into the copper bath. When the copper de- 
posit has acquired the desired thickness, the plate is further 
strengthened by backing with stereotype metal. 

To coat wood, etc., with a galvanoplastic deposit of copper. — The 
absolutely dry objects are first immersed in melted wax, parafine 
or ceresine, and when thoroughly impregnated taken out, and, 
after draining off, allowed to cool. As the impregnating material 
contracts in cooling, the surface of the object is thereby freed from 
an excess of it. For this reason the material used for impreg- 
nating should not be made hotter than absolutely necessary, be- 
cause the hotter it is, the stronger the contraction or shrinkage. 
However, as by this contraction the edges and portions of the 
surface may become denuded of impregnating material, and thus 
be liable to be attacked by the acid copper bath, it is advisable to 
coat the objects, after cooling, with an acid-resisting gutta-percha 
lacquer prepared by dissolving 5 to 10 parts, by weight, of gutta- 
percha cuttings in a mixture of 50 parts each of benzine and 
chloroform. Keep the solution in a wide-mouthed glass bottle 
provided with a well-fitting cork, and apply it with a brush. 
The solution being very inflammable it should not be used near 
an open flame. 

Wooden handles of surgical instruments, etc., may be protected 
from the attack of the acid copper bath by coaling them with a 
solution of wax or paraffine in ether, the latter after evaporating 
leaving a thin layer of wax upon the object. 

The articles thus prepared are black-leaded or metallized by 
Parkes's or one of the methods previously given, and brought into 
the copper bath. 

The mercury vessels of thermometers for vacuum and distilling 
apparatus are surrounded by a thick copper deposit to protect them 
from injury by mechanical force. The metallization of glass, 
porcelain, clay, terra-cotta, etc., is effected in the same manner as 
above described. 

Galvanoplastic operations in iron. — Under " Deposition of Iron," 
page 266, the galvanoplastic production of heavy deposits of iron 



314 ELECTRO-DEPOSITION OF METALS. 

has already been referred to, it being there, also, mentioned, that 
according to the researches of various authors, a neutral solution of 
If ozs. of ammonio-ferrous sulphate in 1 quart of water is best 
adapted for the purpose, whilst Klein recommends a solution of 
equal parts of ferrous sulphate and sulphate of magnesia. To 
obtain an any way successfully iron electrotype from an original, 
for instance, from a copper-plate, which should previously be 
oiled and then coated, by means of sulphuretted hydrogen, with 
a thin layer of sulphide of silver, the following conditions have 
to be fulfilled : The bath must be kept absolutely neutral accord- 
ing to one of the methods given on page 267, under formulae III 
and IV. Further, the current-strength must be so regulated that 
absolutely no evolution of gas on the object is perceptible, and 
the distance of the anodes from the objects, which in the begin- 
ning of the operation may be If inches, must, according to Stam- 
mer, be gradually decreased to 0.19 inch. Furthermore, in the 
beginning of the operation the plates must at least every half 
hour be taken from the bath and rinsed off with a strong jet of 
water to remove adhering bubbles, the same object being attained 
by others by brushing the plates over with a feather. While out 
of the bath the plates must not be allowed to dry, as the fresh 
layers would not adhere to the places which have become dry. 
Now, even by strictly fulfilling the above-mentioned conditions, 
a faultless electrotype will be obtained only in one case out of 
five, this fact being mentioned in order to prevent practical electro- 
platers from wasting time and labor upon this process, which has 
not yet been sufficiently investigated and worked out. However, 
the interesting conditions for the production of heavy iron de- 
posits present a field of research and observation to those who 
need not follow galvanoplasty for a living. In making such re- 
searches it should be especially observed whether useful heavy 
deposits can be obtained from iron baths in motion. 

Galvanoplastie operations in nickel. — Though by the electro- 
deposition of nickel, electrotypes are rendered fit for printing 
with metallic colors, which attack copper, and their power of re- 
sisting wear is increased, the latter advantage can to the fullest 
extent be obtained only by a thick deposit. However, this always 
alters the design somewhat, especially the fine hatchings, this 



G ALV ANOPL A STY. 315 

being the reason why in electro-nickeling electrotypes a deposit 
of medium thickness is, as a rule, not exceeded. If a hard nickel 
surface is desired, without injury to the fine lines of the design, 
the layer of nickel has to be reproduced by galvanoplasty, and 
the deposit of nickel strengthened in the copper bath. 

But upon black-leaded gutta-percha or wax moulds a nickel 
deposit can only be obtained in fresh baths ; the deposit, how- 
ever, is faultless only in rare cases, it generally showing holes in 
the depressions. Hence the object has to be attained in a round- 
about way, the mode of procedure being as follows : An impres- 
sion of the original is taken in gutta-percha or wax and from this 
impression a positive cliche in copper is made. The latter is then 
silvered, the silvering iodized as previously described, and a nega- 
tive in copper is then prepared from this positive. The negative 
is again silvered, iodized, and then brought into a nickel bath 
where it receives a deposit of the thickness of stout writing paper ; 
it is then rinsed in water, and the deposit immediately strengthened 
in the acid copper bath ; for the rest it is treated like ordinary 
copper deposits. Nickel electrotypes thus made are almost in- 
destructible. 

Galvcmoplastic operations in silver and gold. — The preparation 
of reproductions in silver and gold also presents many difficulties. 
While copper is separable in a compact state from its sulphate 
solution, silver and gold have to be reduced from their double 
salt solutions — potassium silver cyanide and potassium auric 
cyanide. However, these alkaline solutions attack moulds of fatty 
substances, such as wax and stearine, consequently also plaster-of- 
Paris moulds impregnated with these substances, as well as gutta- 
percha and gelatine. Hence, only metallic moulds can be advan- 
tageously used except the end is to be attained in a roundabout 
way, that is, by first coating the mould with a thin film of copper, 
strengthening this in the silver or gold bath and finally dissolving 
the film of copper with very dilute nitric acid. 

The double salt solutions mentioned above require a well con- 
ducting surface such as cannot be readily prepared by black-lead- 
ing, a further reason why metallic moulds are to be preferred. 
The simplest way for the galvanoplastic reproduction in gold or 
silver of surfaces not in high relief or undercut, is to cover the 



316 ELECTRO-DEPOSITION OF METALS. 

object with lead, silver, or gold foil and pressing softened gutta- 
percha upon it ; the foil yields to the pressure without tearing 
and adheres to the gutta-percha so firmly that it can be readily 
separated together with it. Galvanoplastic reproductions in the 
noble metals are so seldom made in practice that it is not necessary 
to give further details. The composition of the baths generally 
used is as follows : — 

Bath for galvanoplastic operations with silver. — Fine silver (in 
the form of silver cyanide or chloride of silver), If ozs., 98 per 
cent, potassium cyanide 5J ozs., water 1 quart. 

Bath for galvanoplastic operations with gold : Fine gold (in the 
form of neutral chloride of gold) 1 oz., potassium cyanide 3J ozs., 
water 1 quart. 



CHAPTER XV. 

COLORING, PATLNIZING, OXIDIZING, ETC., OF METALS. 

LACQUERING. 

Though, strickly speaking, these operations do not form a 
part of a work on the electro-deposition of metals, they require to 
be mentioned, since the operator is frequently forced to make 
use of one or the other method in order to furnish basis-metals 
or electro-deposits in certain shades of colors ordered. 

By patina is understood the beautiful green color, antique 
statues, and other art-works of bronze acquire by long exposure 
to the action of the oxygen, carbonic acid, and moisture of the 
air, whereby a thin layer of copper carbonate is formed upon 
them. It has been sought to accelerate by chemical means the 
formation of the patina thus slowly produced by the influence of 
time, and the term patinizing has been applied to this artificial 
production of colors. Without drawing a strict line as to which 
processes have to be considered as coloring, and which as patiniz- 
ing, the most approved methods for changing the color of the 
metals or of the deposits will be given. 



COLORING, ETC., OF METALS. — LACQUERING. 317 

1. Coloring of copper. — All shades from the pale-red of copper 
to a dark chestnut brown can be obtained by superficial oxidation 
of the copper. For small objects it suffices to heat them uniformly 
over an alcohol flame ; with larger objects a more uniform result 
is obtained by heating them in oxidizing fluids or brushing them 
over with an oxidizing paste, the best results being obtained with 
a paste prepared, according to the darker or lighter shade desired, 
from 2 parts of ferric oxide and 1 part of black-lead, or 1 part 
each of ferric oxide and black-lead, with alcohol or water. Apply 
the paste as uniformly as possible with a brush and place the 
object in a warm place (oven or drying chamber). The darker 
the color is to be the higher the temperature must be, and the 
longer it must act upon the object. When sufficiently heated the 
dry powder is removed by brushing with a soft brush, and the 
manipulation repeated if the object does not show a sufficiently 
dark tone. Finally the object is rubbed with a soft linen rag 
moistened with alcohol, or brushed with a soft brush and a few 
drops of alcohol until completely dry, and then with a brush 
previously rubbed upon pure wax. The more or less dark shade 
produced in this manner is very warm and resists the action of 
the air. 

Brown color upon copper is obtained by the application to the 
thoroughly cleansed surface of the object of a paste of verdigris 
3 parts, ferric oxide 3, sal ammoniac 1, and sufficient vinegar, 
and heating until the applied mixture turns black ; the object is 
then washed and dried. By the addition of some blue vitriol the 
color may be darkened to chestnut brown. 

A brown color is also obtained by brushing to dryness with a 
hot solution of 1 part of potassium nitrate, 1 of common salt, 2 
of ammonium chloride, and 1 of liquid ammonia in 95 of vinegar. 
A warmer tone is, however, produced by the method introduced 
in the Paris Mint, which is as follows : Powder and mix inti- 
mately equal parts of verdigris and sal ammoniac. Take a heap- 
ing tablespoon ful of this mixture and boil it with water in a 
copper kettle for about twenty minutes and then pour off the 
clear fluid. To give copper objects a bronze-like color with this 
fluid pour part of it into a copper pan ; place the objects sepa- 
rately in it upon pieces of wood or glass so that they do not touch 



318 ELECTKO-DEPOSITION OF METALS. 

each other, or come in contact with the copper pan, and then boil 
them in the liquid for a quarter of an hour. Then take the objects 
from the solution, rub them dry with a linen cloth and brush them 
with a waxed brush. 

A red-brown color on copper is produced in China by the appli- 
cation of a paste of verdigris 2 parts, cinnabar 2, sal ammoniac 5, 
and alum 5, with sufficient vinegar, heating over a coal fire, wash- 
ing and repeating the process. 

Copper is colored blue-black by dipping the object in a hot solu- 
tion of 11 \ drachms of liver of sulphur in 1 quart of water, 
moving it constantly. Blue-gray shades are obtained with more 
dilute solutions. It is difficult to give definite directions as to 
the length of time the solution should be allowed to act, since this 
depends on its temperature and concentration. With some expe- 
rience the correct treatment, however, will soon be learned. 

The so-called cuivre fume is produced by coloring the copper 
or coppered objects blue-black with solution of liver of sulphur, 
then rinsing, and finally scratch-brushing them, whereby the 
shade becomes somewhat lighter. From raised portions which 
are not to be dark, but are to show the color of copper, the color- 
ation is removed by polishing upon a felt disk or bob. 

Black color upon copper is produced by a heated pickle of 2 
parts of arsenic acid, 4 of concentrated muriatic acid, 1 of sul- 
phuric acid of 66° Be., and 24 of water. 

Dead-black on copper. — Brush the object over with a solution 
of 1 part of platinum chloride in 5 of water, or dip it in the solu- 
tion. A similar result is obtained by dipping the copper object 
in a solution of nitrate of copper or of manganese, and drying 
over a coal fire. These manipulations are to be repeated until 
the formation of a uniform dead-black. 

Imitation of genuine patina. — Repeatedly brush the objects with 
solution of sal ammoniac in vinegar ; the action of the solution 
being accelerated by the addition of verdigris. A solution of 9 
drachms of sal ammoniac and 2J drachms of potassium binoxalate 
in 1 quart of vinegar acts still better. When the first coating is 
dry, wash the object, and repeat the manipulations, drying and 
washing after each application, until a green patina is formed. It 
is best to bring the articles after being brushed over with the 
solution into a hermetically closed box upon the bottom of which 



COLORING, ETC., OF METALS. — LACQUERING. 319 

a few shallow dishes containing very dilute sulphuric or acetic 
acid and a few pieces of marble are placed. Carbonic acid being 
thereby evolved and the air in the box being kept sufficiently 
moist by the evaporation of water, the conditions required for the 
formation of genuine patina are thus fulfilled. If the patina is 
to show a more bluish tone, brush the object with a solution of 
4 J ozs. of ammonium carbonate and 1J ozs. of sal ammoniac in 
1 quart of water, to which a small quantity of gum tragacanth 
may be added. 

To produce a steel-gray color upon copper immerse the clean 
and pickled objects in a heated solution of chloride of antimony 
in hydrochloric acid. By using a strong electric current the 
objects may also be coated with a steel-gray deposit of arsenic in 
a heated arsenic bath. 

For coloring copper dark steel-gray, a pickle consisting of 1 
quart of hydrochloric acid, 0.125 quart of nitric acid, \\ ozs. of 
arsenious acid, and a like quantity of iron filings is recommended. 

Various colors upon massive copper. — First draw the object 
through a pickle composed of sulphuric acid 60 parts, hydro- 
chloric acid 24.5, and lamp-black 15.5; or of nitric acid 100 
parts, hydrochloric acid 1J, and lamp-black J. Then dissolve 
in a quart of water 4 J ozs. of sodium hyposulphite, and in 
another quart of water 14 J drachms of blue vitriol, 5 J drachms 
of crystallized verdigris, and 7| grains of sodium arsenate. Mix 
equal volumes of the two solutions, but no more than is actually 
necessary for the work in hand, and heat to between 167° and 
176° F. By dipping articles of copper, brass, or nickel in the hot 
solution they become immediately colored with the colors men- 
tioned below, one color passing within a few seconds into the 
other, and for this reason the eifect must be constantly controlled 
by frequently taking the objects from the bath. The colors suc- 
cessively formed are as follows : — 

Upon copper : Upon brass : Upon nickel : 

Orange, Golden yellow, Yellow, 

Terra-cotta, Lemon color, Blue, 

Red (pale), Orange, Iridescent. 
Blood red, Terra-cotta, 
Iridescent. Olive green. 



320 ELECTRO-DEPOSITION OF METALS. 

Some of these colors being not very durable have to be pro- 
tected by a coat of lacquer or paraffine. It is further necessary 
to diligently move the objects so that all portions acquire the 
same color. The bath decomposes rapidly, and hence only suffi- 
cient for 2 or 3 hours' use should be mixed at one time. 

2. Coloring of brass and bronzes. — Most of the directions given 
for coloring copper are also available for brass and bronzes, 
especially those for the production of the green patina, and the 
oxidized tones by a mixture of ferric oxide and black lead. 

Many colorations on brass, however, are effected only with 
difficulty, and are partially entirely unsuccessful, as for instance, 
coloring black with liver of sulphur. As a pickle for the pro- 
duction of a 

Lustrous black on brass, the following solution may be used : 
Dissolve freshly precipitated carbonate of copper, while still 
moist, in strong liquid ammonia, using sufficient of the copper 
salt so that a small excess remains undissolved, or in other words, 
that the ammonia is saturated with copper. The carbonate of 
copper is prepared by mixing hot solutions of equal parts of blue 
vitriol and of soda, filtering off, and washing the precipitate. 

Dilute the solution of the copper salt in ammonia with one- 
fourth its volume of water, add 31 to 46 grains of black-lead, 
and heat to between 95° and 104° F. Place the clean and 
pickled objects in this pickle for a few minutes, until they show 
a full black shade, then rinse in water, dip in hot water and dry 
in sawdust. The solution soon spoils and, hence, no more than 
required for immediate use should be prepared. 

Another method of coloring brass black has been given under 
" Deposition of Arsenic," p. 270. 

Urqnhart states that clean brass and copper may be covered 
with a firmly adherent black coating by placing them very near 
to the flames of burning straw. It will not rub off, and may be 
polished with a soft cloth. 

Steel-gray on brass is obtained by the use of a mixture of 1 lb. 
of strong hydrochloric acid with 1 pint, of water, to which are 
added 5J ozs. of iron filings and a like quantity of pulverized 
antimonic sulphide. 

Hydrochloric acid compounded with arsenious acid is also 



COLORING, ETC., OF METALS. — LACQUERING. 321 

recommended for this purpose. The mixture is brought into a 
lead vessel, and the objects dipped in it should come in contact 
with the lead of the vessel, or be wrapped around with a strip of 
lead. 

A gray color with a bluish tint upon brass is produced with 
solution of antimonious chloride (butter of antimony) while a 
pure steel-gray color is obtained with a hot solution of arsenious 
chloride with a little water. 

Straw color to brown through golden yellow and tombac color on 
brass may be obtained with solution of carbonate of copper in 
caustic soda lye. Dissolve 5.25 ozs. of caustic soda in 1 quart of 
water, and add 1} ozs. of carbonate of copper. By using the 
solution cold, a dark golden yellow is first formed, which finally 
passes through pale brown into dark brown with a green lustre ; 
with the hot solution the coloration is more rapidly effected. 

A color resembling gold or brass is, according to Dr. Kayser, 
obtained as follows : Dissolve 8 J drachms of sodium hyposulphite 
in 17 drachms of water, and add 5.64 drachms of solution of anti- 
monious chloride. Heat the mixture to boiling for some time, 
then filter off the red precipitate formed, and after washing it several 
times upon the filter with vinegar, suspend it in 2 or 3 quarts of 
hot water ; then heat and add concentrated soda lye until solu- 
tion is complete. In this hot solution dip the clean and pickled 
brass objects, removing them frequently to see whether they have 
acquired the desired coloration. The articles become gray by 
remaining too long in the bath. 

Brown color, called bronze Barbedienne, on brass. — This beauti- 
ful color may be produced as follows : Dissolve by vigorous shak- 
ing in a bottle, freshly prepared arsenious sulphide in spirit of sal 
ammoniac, and compound the solution with antimonious sulphide 
until a slight permanent turbidity shows itself, and the fluid has 
acquired a deep yellow color. Heat the solution to 95° F., and 
suspend the brass objects in it. They become at first golden 
yellow and then brown, but as they come from the bath with a 
dark dirty tone, they have to be several times scratch-brushed to 
bring out the color. If, after using it seve.al times, the solution 
fails to work satisfactorily, add some antimonious sulphide. The 
2i 



322 ELECTRO-DEPOSITION OF METALS. 

solution decomposes rapidly, and should be prepared fresh every 
time it is to be used. 

By this method only massive brass objects can be colored brown ; 
to brassed zinc and iron the solution imparts brown-black tones, 
which however are also quite beautiful. 

Upon massive brass, as well as upon brassed zinc and iron 
objects, bronze Barbedienne may be produced as follows : Mix 
3 parts of red sulphide of antimony (stibium sulfur at um auranti- 
anum) with 1 part of finely pulverized bloodstone, and triturate 
the mixture with ammonium sulphide to a not too thickly-fluid 
pigment. Apply this pigment to the objects with a brush, and 
after allowing it to dry in a drying chamber, remove the powder 
by brushing with a soft brush. 

In Paris bronze articles are colored dead-yellow or clay-yellow 
to dark-brown by first brushing the pickled and thoroughly rinsed 
objects with dilute antimony bisulphide, and after drying, re- 
moving the coating of separated sulphur by brushing. Dilute 
solution of sulphide of arsenic in ammonia is then applied, the 
result being a color resembling mosaic gold. The more frequently 
the arsenic solution is applied, the browner the color becomes. By 
substituting for the arsenic solution one of sulphide of antimony 
in ammonia or ammonium sulphide, colorations of a more reddish 
tone are obtained. 

Violet- and corn-flower blue upon brass may be produced as 
follows : Dissolve in 1 quart of water, 4J ozs. of sodium hypo- 
sulphite, and in another quart of water, 1 oz. 3} drachms of 
crystallized sugar of lead, and mix the solutions. Heat the 
mixture to 176° F., and then immerse the articles, moving them 
constantly. First a gold-yellow coloration appears, which how- 
ever soon passes into violet and blue, and, if the bath be allowed 
to act further, into green. The action is based upon the fact that 
in an excess of hyposulphite of soda, solution of hyposulphite of 
lead is formed, which decomposes slowly and separates sulphide 
of lead, which precipitates upon the brass objects and produces 
the various lustrous colors. 

Similar lustrous colors are obtained by dissolving 2.11 ozs. of 
pulverized tartar in 1 quart of water, and 1 oz. of chloride of 
tin in J pint of water, mixing the solutions, heating, and pouring 



COLORING, ETC., OF METALS. LACQUERING. 323 

the clear mixture into a solution of 6.34 ozs. of sodium hyposul- 
phite in 1 pint of water. Heat this mixture to 176° F., and 
immerse the pickled brass objects. 

Ebermayer's experiments in coloring brass. — In the following the 
results of Ebermayer's experiments are given. In testing the 
directions, the same results as those claimed by Ebermayer were 
not always obtained ; the variations are given in parenthesis. 

I. Blue vitriol 8 parts by weight, crystallized sal ammoniac 2, 
water 100, give by boiling a greenish color. (The color is olive- 
green, and useful for many purposes. The coloration however 
succeeds only upon massive brass, but not upon brassed zinc.) 

II. Potassium chlorate 10 parts by weight, blue vitriol 10, water 
1000, give by boiling a brown-orange to cinnamon-brown color. 
(Only a yellow-orange color could be obtained.) 

III. By dissolving 8 parts by weight of blue vitriol in 1000 
of water, and adding 100 of caustic soda until a precipitate is 
formed, and boiling the objects in the solution, a gray-brown 
color is obtained, which can be made darker by the addition of 
colcothar. (Stains are readily formed. Brassed zinc acquires a 
pleasant pale-brown.) 

IV. With 50 parts by weight of caustic soda, 50 of sulphide of 
antimony, and 500 of water, a pale fig-brown color is produced. 
(Fig-brown could not be obtained, the shade being rather dark 
olive green.) 

V. By boiling 400 parts by weight of water, 25 of sulphide of 
antimony and 60 of calcined soda, and filtering the hot solution, 
mineral kermes is precipitated-. By taking of this 5 parts by 
Aveight and heating with 5 of tartar, 400 of water, and 10 of 
sodium hyposulphite, a beautiful steel-gray is obtained. (The re- 
sult is tolerably sure and good.) 

"VI. Water 400 parts by weight, potassium chlorate 20, nickel 
sulphide 10, give, after boiling for some time, a brown color, which, 
however, is not formed if the sheet has been pickled. (The brown 
color obtained is not very pronounced.) 

VII. Water 250 parts by weight, potassium chlorate 5, carbonate 
of nickel 2, and sulphate of ammonium and nickel 5, give after 
boiling for sometime, a brown-yellow color, playing into a maguifi- 
cent red. (The results obtained were only indifferent.) 



324 ELECTRO-DEPOSITION OF METALS. 

VIII. Water 250 parts by weight, potassium chlorate 5, and sul- 
phate of nickel and ammonium 10, give a beautiful dark brown. 
(Upon massive brass a good dark-brown is obtained. The for- 
mula, however, is not available for brassed zinc.) 

3. Coloring zinc. — The results obtained by coloring zinc directly 
according to existing directions cannot be relied on, and it is, 
therefore, recommended to first copper the zinc and then color 
the coppering. Experiments in coloring zinc black with alcoholic 
solution of chloride of antimony according to Dullas's process gave 
no useful results. Puscher's method is better ; according to it the 
objects are dipped in a boiling solution of 5.64 ozs. of pure green 
vitriol and 3.17 ozs. of sal ammoniac in 2J quarts of water. The 
loose black precipitate deposited upon the objects is removed by 
brushing, the object again dipped in the hot solution and then 
held over a coal fire until the sal ammoniac evaporates. By re- 
peating the operation three or four times a firmly adhering black 
coating is formed. To color zinc black with nitrate of manga- 
nese, as proposed by Neumann, is a tedious operation, it requiring 
to be repeated seven or eight times. It is done by dipping the 
object in a solution of nitrate of manganese and heating over a 
coal fire, the manipulations being repeated until a uniform dead- 
black is formed. 

By suspending zinc in a nickel bath slightly acidulated with 
sulphuric acid, a firmly adhering blue-black coating is, after some 
time, formed without the use of a current. This coating is use- 
ful for many purposes. A similar result is attained by immers- 
ing the zinc objects in a solution of 2.11 ozs. of the double 
sulphate of nickel' and ammonium and a like quantity of sal 
ammoniac in 1 quart of water. The articles become first dark 
yelloiv, then, successively, broivn, purple-violet, and indigo-blue, 
and stand slight scratch-brushing and polishing. 

A gray coating on zinc is obtained by a deposit of arsenic in a 
heated bath composed of 2.82 ozs. of arsenious acid, 8.46 drachms 
of sodium pyrophosphate, and If drachms of 98 per cent, potassium 
cyanide and 1 quart of water. A strong current should be used 
so that a vigorous evolution of hydrogen is perceptible. Platinum 
sheets or carbon plates are used as anodes. 

A sort of bronzing on zinc is obtained by rubbing it with a 



COLORING, ETC., OF METALS. LACQUERING. 325 

paste of pipe-clay to which has been added a solution of 1 part 
by weight of crystallized verdigris, 1 of tartar, and 2 of crystal- 
lized soda. 

Red-brotcn color on zinc. — Rub with solution of chloride of 
copper in liquid ammonia. 

Yellow-brown shades on zinc. — Rub with solution of chloride of 
copper in vinegar. 

4. Coloring of iron. — The browning of gun-barrels is effected 
by the application of a mixture of equal parts of butter of 
antimony and olive oil. Allow the mixture to act for 12 to 14 
hours, then remove the excess with a w T oolen rag and repeat the 
application. When the second application has acted for 12 to 24 
hours, the iron or steel will be coated with a bronze-colored layer 
of ferric oxide with antimony, which resists the action of the air 
and may be made lustrous by brushing with a waxed brush. 

A lustrous black on iron is obtained by the application of 
solution of sulphur in spirits of turpentine prepared by boiling 
upon the water bath. After the evaporation of the spirits of 
turpentine a thin layer of sulphur remains upon the iron, which, 
on heating the object, immediately combines with the metal. 

By another method the cleansed and pickled iron objects are 
coated, w T hen dry, with linseed oil and heated to a dark red. If 
pickling is omitted, the coating with linseed oil and heating may 
have to be repeated two or three times. 

According to Meritens, a lustrous black on iron is obtained by 
placing the articles as anode in distilled water heated to 158° F., 
and using an iron plate as cathode. A layer of ferroso-ferric 
oxide is formed, which, however, can be obtained in a firmly ad- 
hering state only upon wrought-iron. The lustre appears by 
brushing with a soft waxed brush. The current conducted into 
the bath must just be strong enough to decompose the water Avith- 
out perceptible evolution of gas. 

According to Bottger a durable blue on iron and steel may be 
obtained by dipping the article in a J per cent, solution of red 
prussiate of potash mixed with an equal volume of a J per cent, 
ferric chloride solution. 

A brown-black coating with bronze lustre on iron is obtained by 
heating the bright iron objects and brushing them over with con- 



326 EEECTBO-DEPOSITICLV OF METALS. 

centrated solution of potassium bichromate. When dry, heat 
them over a charcoal fire and wash until the water running off 
shows no longer a yellow color. Repeat the operation twice or 
three times. A similar coating is obtained by heating the iron 
objects with a solution of 10 parts by weight of green vitriol and 
1 part of sal ammoniac in water. 

To give iron a silvery appearance with high lustre. — Scour the 
polished and pickled iron objects with a solution prepared as fol- 
lows : Heat moderately 1 J ozs. of chloride of antimony, 0.35 oz. 
of pulverized arsenious acid, 2.82 ozs. of elutriated blood-stone 
with 1 quart of 90 per cent, alcohol upon a water bath for half 
an hour. Partial solution takes place. Dip into this fluid a tuft 
of cotton and go over the iron portions, using slight pressure. 
A thin film of arsenic and antimony is thereby deposited which 
is the more lustrous, the more carefully the iron had been previ- 
ously polished. 

5. Coloring of tin. — A bronze-like patina on tin may be obtained 
by brushing the object over with a solution of If ozs. of blue 
vitriol and a like quantity of green vitriol in 1 quart of water, 
and moistening the object when dry with a solution of 3J ozs. of 
verdigris in 10J ozs. of vinegar. When dry, polish the object 
with a soft waxed brush and some ferric oxide. The coating thus 
obtained being not especially durable must be protected by a coat- 
ing of lacquer. 

Durable and very warm sepia-brown tone upon tin and its 
alloys. — Brush the object over with a solution of 1 part of platinum 
chloride in 10 of wat:r, allow the coating to dry, then rinse in 
water, and, after again drying, brush with a soft brush until the 
desired brown lustre appears. 

A dark coloration is also obtained with ferric chloride solution. 

6. Coloring of silver. — See "Silvering," p. 228. 

Lacquering. 

In the electro-plating industry recourse is frequently had to 
lacquering in order to make the deposits more resistant against 
atmospheric influences, or to protect artificially prepared colors, 
patinas, etc. Thin colorless shellac solution which does not affect 



COLORING, ETC., OF METALS. LACQUERING. 327 

the color of the deposit or of the patinizing is, as a rule, employed, 
while in some cases colored lacquers are used to heighten the tone 
of the deposit, as, for instance, gold lacquer for brass. 

The lacquer is applied by means of a fine flat fitch-brush, the 
object having previously been heated hand-warm. After lacquer- 
ing the object is dried in an oven at a temperature of between 
140° and 158° F., whereby small irregularities are adjusted, and 
the layer of lacquer becomes transparent, clear, and lustrous. 

If such lacquer has to be reduced only absolute alcohol free 
from water should be used for the purpose, since alcohol contain- 
ing water makes the coating of lacquer dull and non-transparent. 

Recently a dipping lacquer under the name of zapon has been 
introduced in commerce. This lacquer is manufactured by the 
Frederick Crane Chemical Co., Short Hills, N". J. It represents 
a clear almost colorless fluid of the consistency of collodion, and 
smells somewhat like fruit ether. According to G. Buchner, it 
consists essentially of a solution of celluloid in a mixture of amyl 
acetate and acetone. Of the last two bodies the " thinning fluid" 
accompanying the preparation, also consists. This lacquer can 
be highly recommended, its superiority being due to the favorable 
properties of the celluloid. The transparent, colorless coat ob- 
tained with zapon can be bent with the metallic sheet to which it 
has been applied without cracking. It is so hard that it can 
scarcely be scratched with the finger-nail, shows no trace of sticki- 
ness, and is perfectly homogeneous even on the edges. This 
favorable behavior is very likely due to the slow evaporation of 
the solvent and the fact that the lacquer quickly forms a thickish, 
tenacious layer, which, though moved with difficulty, is not en- 
tirely immobile. Another advantage of zapon — especially as 
regards metallic objects — is that the coating, in consequence of its 
physical constitution, preserves the character of the basis. In 
accordance with the nature of celluloid the coating is not sensibly 
affected by ordinary differences in temperature and does not be- 
come dull and non-transparent, as is the case with resins, in con- 
sequence of the loss of molecular coherence. It can be washed 
with soap and water, and protects metals coated with it from the 
action of the atmosphere. Zapon may also be colored but, of 
course, only with coloring substances (mostly analine colors), which 



328 ELECTRO-DEPOSITION OF METALS. 

are soluble in the solvent used for the celluloid. Dipping the 
objects in the zapon being more advantageous than applying it 
with the brush, the manufacturers have constructed a special 
dipping apparatus. 

In conclusion, a few words may be said in regard to the pro- 
cesses by which those magnificent effects are obtained which imitate 
so completely the appearance, freshness, and rich tones of real 
gilding. In general, gold varnish is applied only upon copper and 
its more or less yellow alloys. 

Gold varnishers operate as follows : After the objects have been 
perfectly cleansed, scratch-brushed, and burnished, if necessary, 
they are completely dried in hot sawdust and wiped clean with 
a fine cloth. A light coat of varnish is then applied with a fitch- 
pencil, and all excess of varnish removed or levelled with another 
flat brush of badger-hair or bristles. The two brushes are kept to- 
gether in the same hand, the varnish brush between the thumb 
and first two fingers, while the flat one (without a handle) is held 
between the other fingers and the palm of the hand. In this 
manner there is no interval in the use of the two brushes. The 
varnish is kept in a jelly-pot or other similar vessel across the top 
of which a string has been stretched. This string is intended for 
removing by wiping the excess of varnish taken up by the brush 
or pencil. The varnish which covers the burnished parts of the 
object may be removed with a clean rag moistened with alcohol 
and wrapped round the finger. Another dry cloth finishes the 
drying. Sometimes the burnished parts are also varnished, but 
the operation is very difficult when their surface is considerable. 
Round-ware, polished or burnished, may be varnished in the lathe. 

After the varnish has been applied as uniformly as possible, the 
objects are put in a drying stove heated to between 140° and 175° 
F. The alcohol or essential oils of the varnish are rapidly vola- 
tilized, while the resins or gums melt and cover the objects with 
a glassy lustre. The heat must be sufficient to melt these gums, 
but low enough to avoid burning them. When the operation has 
been well performed, the pieces present a beautiful and uniform 
golden appearance, with no disfiguring red patches, which latter 
indicate an unequal thickness of varnish. 

Varnishers have always at their disposal four varnishes of 



APPARATUS AND INSTRUMENTS. 329 

different shades — red gold, orange yellow-gold, green gold, and 
colorless varnish for mixture. This last is employed for diluting 
the first three and diminishing the depth of their colors. Each 
of these various varnishes gives to copper the gold color peculiar 
to it, and, when mixed, intermediary shades. It often happens 
that the various parts of a large piece are different in composition 
and color, and the varnisher is obliged to impart the same shade 
of gold all over, by skilful combinations of varnishes. He thus 
succeeds in giving the same gold color to half-red copper, and to 
alloys of yellow and green brass. 

But a small quantity of varnish is poured into the varnish pot 
at one time, to prevent it from thickening by evaporation, and, 
after the operation, the residue is poured back into the flask from 
which it was taken, and kept well stoppered. The brushes and 
pencils must be often washed in alcohol, which may afterwards 
be used for diluting thick varnishes. 

These varnishes are made by dissolving various resinous sub- 
stances, like sandarac, benzoin, dragon's blood, elemi, gamboge, 
etc., and tinctorial matters, such as saffron, annotto, alkanet, etc., 
in a mixture of alcohol with essence of lavender or of spikenard. 
All qualities of varnish are to be found, but the more expensive 
are often the more economical. 

To remove the varnish from an imperfectly varnished object 
or from an old one, it is immersed in alcohol or concentrated sul- 
phuric acid or, better still, in a boiling solution of caustic lye. 
The varnishing is then begun anew. 



CHAPTER XVI. 

APPARATUS AND INSTRUMENTS. 

Batteries and dynamo machines. — In addition to the batteries 
and dynamo machines described and illustrated in Part III., 
"Sources of Current," the following recent American types, 
which are especially suitable for electro-plating purposes, should 
be mentioned. 



330 



ELECTRO-DEPOSITION OF METALS. 



Improved Bunsen cell. — Fig. 100 shows an improved type of 
Bunsen cell for nickel plating purposes, where the absence of 




power prevents the use of a dynamo machine. This cell fur- 
nishes a large volume of current, as its internal resistance is low. 
It is an easy battery to set up and keep in working order. The 
batteries are set up by well amalgamating, inside and out, the 
zinc 2, Fig. 101, and placing it in the jar 1. Inside the zinc 

Fie 101. 




place the porous cup 3, and within the porous cup, the carbon 4, 
and then pour nitric acid in the porous cup. In the outer jar 
pour a mixture of 1 part sulphuric acid to 12 of water (pre- 
viously mixed and allowed to cool). This acid mixture should 



APPARATUS AND INSTRUMENTS. 



331 



cover the zinc or be on a level with the liquid in the porous cup. 
When the liquid in the outer jar becomes milky, withdraw it 
with a syringe or siphon, and refill, adding occasionally small 
quantities of nitric acid to the porous cup, and keeping the zinc 
thoroughly amalgamated. To avoid the deleterious fumes of 
nitrous oxide given off while the battery is at work, it should 
be kept in a well-ventilated box or in a shed or cupboard outside 
the work-shop, as described on page 50. 

The new dynamo electric machine manufactured by the Hanson 
& Van Winkle Co., of Newark, New Jersey, is shown in Fig. 102. 

Fig. 102. 




K is the coil of the field magnet; A the revolving armature, and 
C the commutator. BB are the brushes for picking up the cur- 
rents of electricity produced in the armature by revolving in the 
magnetic field and causing them to flow in one direction. The 
current is not produced by friction. I) is the lever to adjust the 
position of the brushes to the commutator. NN&re f inch copper 



332 ELECTRO-DEPOSITION OF METALS. 

rods from the machine to the tank or to the main conductors on 
the wall. The binding post on the machine marked P is joined to 
rods connected with the anodes, while JVis connected to the object 
rods. The rods on the tank should be kept bright with emery paper. 
When but one tank is used make direct connection in the same 
way after getting the speed of the machine satisfactory for the 
maximum amount of work. The current may be decreased for 
small surfaces by moving the handle of the resistance board from 
the point marked " strong," one segment at a time, until it is 
found to answer. The position of the brushes as shown in the 
cut, is the strongest point. By moving to the right or left the cur- 
rent is diminished. A slight change of position of the brushes 
is sometimes an advantage in setting the brushes when running 
on large surfaces to avoid sparks. 

In using the resistance boards, they are put up as near the tank 
as possible — the weak point being used when putting work in the 
tank, and then the strength of current is increased until the power 
required is obtained. 

The proper current for nickel plating on brass or other 
smooth surfaces is when the gas is seen to adhere to the work, 
and there is no tendency to blacken edges. 

The manufacturers of the above described dynamo machine 
claim for it the following advantages : — 

The field magnets have wrought-iron in them, vastly superior 
to cast-iron. The magnets have a round core which, for a given 
amount of wire, is much more powerful. They have a very short 
magnet circuit. The commutator is easily taken off, so as to renew 
the segments, which are made of tempered copper, and are very 
durable. The armature and working parts are away from the 
base, and are fully protected from dirt. The field magnets are 
wound on bobbins, and are easily replaced. The armature is of 
Norway iron, each piece being insulated from its neighbor and 
the steel shaft, which entirely dispenses with cross-currents, and 
avoids heating of the armature core. 

The "American Gian^ dynamo-machine. This machine is 
manufactured by the Zucker & Levett Chemical Company of New 
York. In this dynamo the soft iron field magnet cores are at- 
tached to a semi -cylindrical cast-iron yoke, which is itself screwed 



APPARATUS AND INSTRUMENTS. 333 

to the frame of the machine, so that the pole pieces face one an- 
other. The field magnets are wound in four distinct sections, 
the wire ends of which project. These are brought out and con- 
nected to studs, which are on the outside of the box which forms 
the cover of the dynamo. A sliding switch can be made to pass 
over these studs in succession, and thus cause the exciting current 
to pass round one or more of the four coils at will, thus increasing 
the magnetization of the field magnets, and therefore the output 
of the dynamo in like proportion. The manufacturers claim the 
following advantages for this machine: Impossible to reverse 
current or to overheat ; less power required to run it ; noiseless ; 
no water required to keep it cool ; no sparks ; simplicity in regu- 
lating current ; all parts interchangeable and exposed, so that any 
novice can adjust the parts of machine. Each machine has auto- 
matic oil-cups, saving labor and oiling and preventing journals 
from wearing out so quickly. 

Vats. — These are the vessels to hold the plating solutions. 
Their shape may be either circular, square, or rectangular. They 
should be perfectly tight, impervious to the solutions and unacted 
upon by them. They are made of different materials, stoneware, 
glass, or porcelain vats being best, but they are the most fragile 
and expensive. 

Wooden vats should have their exterior covered with heavy 
coats of varnish or pitch, which resist the action of the baths, or 

Fig. 103. 



with a sheathing of gutta-percha or India-rubber. They are 
sometimes lined with sheet-lead, welded by the gas-process, since 
any kind of tin-solder would be inadmissible. Such vats are 



334 ELECTRO-DEPOSITION OF METALS. 

satisfactory for galvano-plastic operations, provided that the lead 
lining be insulated from the electric circuit. 

As an all-round useful vat there is nothing equal to one of 
enameled iron, such as shown in Fig. 103. It is enameled with a 
white acid-proof enamel and highly recommended for all solu- 
tions. It is made in other shapes and sizes up to 5 J feet long, 24 
inches wide, and 19 inches deep. 

Fig. 104 shows an agate vessel for gold and other solutions. 
This material stands cyanide solutions, acids, etc. 

Fig. 104. 




Slinging wires. — When the objects have been prepared for the 
reception of a deposit of metal, they are hung from the object- 
rod of the vat in the plating solution by lengths of copper wire, 
to which the term "slinging wires" has been applied. They are 
simply suitable lengths of copper wire, of a gauge to suit the work 
in hand, wire of No 20 Birmingham wire gauge (see Chapter 
XIX., " Useful Tables") being generally employed for such light 
work as spoons, forks and table utensils. Wire of a larger diam- 
eter should be employed for large and heavy goods. The im- 
mersed ends of these wires becoming coated with the metal which 
is being deposited, they should be carefully set aside each time 
after use, and when the deposit gets thick, it should be stripped 
oif in stripping acid, the wire afterwards annealed and straight- 
ened for future use. 

Conducting wires. — These are the metallic wires, bands, spirals, 
or ribbons, which carry the electric current to the baths. The 
conducting wires are either employed with their natural metallic 
surface, or are covered with some insulating, or poorly conduct- 
ing substance, such as cotton, silk, India-rubber, gutta-percha, 
and various varnishes. It is evident that covered wires should 



APPARATUS AND INSTRUMENTS. 



335 



be bare and clean at their extremities where they are connected 
with the battery and with the anodes or objects to be coated. 
Wires of pure well-annealed copper possess the best conducting 
power, and should have a sectional area capable of carrying the 
maximum quantity of current without offering appreciable resist- 
ance. Cables should be chosen where a large volume of current 
must be carried, they being more flexible than wire of a large 
size, and can be more easily laid. 

Insulated wires raav come in contact with each other without 



Fig. 105. 




336 



ELECTRO-DEPOSITION OF METALS. 



inconvenience. Such, however, is not the case with bare wires ; 
because the electricity will pass through the shortest circuit, and 
will not go through the bath if the two wires are in metallic con- 
tact. Such contact should, therefore, be carefully avoided. 

Binding posts and rod, connections. — In addition to the forms of 
binding screws shown in Figs. 39, 40 and 41, p. 89, the follow- 
ing are given : Nos. 1 and 2, Fig. 105, are rod connections for 
tanks ; No. 3 is a wire connection for cutting in branch between 
batteries or dynamos and tanks ; No. 4, wire connection for two or 
more wires, and No. 5, binding post for resistance board or dynamo. 



Fiz. ] 




APPARATUS AND INSTRUMENTS. 337 

Lathe for polishing silver plate and silver. — A good lathe for 
this purpose is represented in Fig. 106, which shows an American 
patent foot-lathe adapted for grinding and polishing. This lathe 
stands 3 feet 9 inches from floor to centre of spindle, has a 26 inch 
driving wheel, turned with grooves for three different speeds, and 
will run the spindle easily at from 300 to 3000 revolutions per 
minute. The spindle B is suitable for leather, muslin, and 
swansdown bobs, buffs, and mops. This can be unscrewed and 
replaced by the spindle C, which is furnished with a taper screw 
for the bosses of circular brushes. 

Scratch-brushes. — The various forms of scratch-brushes have 
already been described and illustrated on page 103. In addition 

Fig. 107. Fig. 108. 





the following may be mentioned : Swing brushes for frosting or 
satin finish (Fig. 107), with four knots of medium brass or steel 
wire, and the plater's lathe goblet scratch-brush, Fig. 108. 

Dipping baskets. — These are used for dipping large numbers 
of small articles at a time. Figs. 109, 110, 111, and 112 repre- 
sent different forms of glazed stoneware dipping baskets such as 
are generally used, though some platers prefer a platinum gauze 
cage. 

Bmshes. — A definition of these instruments is unnecessary; 
and we shall simply indicate the various kinds suitable to the 
different operations. 

The fire-gilder employs, for equalizing the coating of amalgam, 
a long-handled brush, the bristles of which are long and very 
stiff. 

22 



338 



ELECTRO-DEPOSITION OF METALS. 

Fig. 109. Fig- HO. 





Fig. 111. 



Fig. 112. 





The electro-gilder uses a brush (Fig. 113), with long and 
flexible bristles. 

For scouring with sand and pumice-stone alloys containing 
nickel, such as German silver, which are difficult to cleanse in 
acids, the preceding brush with smaller and stiffer bristles is used 
(Fig. 115). 



Fig. 113. 



Fig. 114. 



Fig. 115. 




The gilder of watch- works has an oval brush (Fig. 114), with 
stiff and short bristles for graining the silver. 

The galvanoplastic operator, for coating moulds with black- 



APPARATUS AND INSTRUMENTS. 339 

lead, besides a Dumber of pencils, uses also three kinds of brushes 
— the watchmaker's (Fig. 115), a hat brush, and a blacking 
brush. 

The bronzer uses all kinds of brushes. 

Brushes are perfectly freed from adherent grease by washing 
with benzine or bisulphide of carbon. 

Kettles and boiling pans. — These are of various shapes, hemi- 
spherical or with flat bottom, and are made of different materials 
(Figs. 116 and 117). 

Fig. 116. Fig. 117. 



g-~ S> 




Those of copper are employed for whitening with silver and 
cream of tartar. Cast- and sheet-iron are preferable for cleansing 
with caustic alkalies or for evaporating residues, and those of 
stoneware heated on sand or water baths for desilvering (stripping), 
or for giving a dead lustre to copper in warm acids. 

Cast-iron enamelled kettles are used for hot baths of copper, 
silver, gold, and platinum. 

Notwithstanding their enamel, these vessels become gradually 
impregnated with the solutions they have held, and it is dangerous 
to employ them for different kinds of baths. Thus an enamelled 
kettle, which has been used for silvering, will not be suitable, 
even after the most thorough washing, for a gold bath, as the gild- 
ing will certainly be white or green, according to the quantity of 
silver retained by the vessel. 

Stirring rods. — These are rods made of various materials, and 
are employed for mixing together liquids or paste, or liquids and 
pastes, or solids with liquids, or various solids in the dry state. 
Their length and thickness should be suited to the volumes to be 
mixed. 

Suitable stirring rods are those which have no chemical action 
upon the substances with which they are brought in contact ; 




340 ELECTRO-DEPOSITION OF METALS. 

neither should they become impregnated with them. Rods of 
glass, stoneware, or porcelain are decidedly the best. Wood and 
most metals should be avoided, because the former is absorbent 
and the latter are corroded and easily oxidized. 

The operator should always have near at hand a complete as- 
sortment of glass stirrers of various sizes, and with fused or 
rounded ends, in order not to scratch the vessels in which he 
operates. 

Glass balloons and flasks. — These are spheres of thin blown 
glass, Fig. 118, with necks of various dimensions, in length and 
diameter. They are employed for heating acids, dis- 
lig. 118. solving metals, and a great many other uses. They 
should be placed upon triangular supports of iron, and 
at a certain distance from the fire, from the direct 
action of which they are to be protected by the inter- 
vention of a piece of wire gauze or its equivalent. 
The thinner they are the more easily they bear sudden 
changes of temperature. They are preferable to por- 
celain evaporating dishes for dissolving gold, because 
there is much less danger of losing a part of the product by 
spurting. 

Evaporating dishes or capsules. — These are usually vessels of 
porcelain, and are intended to bear a high temperature. The 
best are thin and uniformly so. Like glass flasks, they should 
be supported above the fire upon an iron stand and wire-gauze. 
As far as practicable they should be gradually heated and cooled. 
When taken from the fire, they should be placed upon rings made 
of plaited straw. They are made with or without lips, and some 
have a socket for a wooden handle. Glass evaporating dishes are 
not durable. 

Glass jars. — These are glass vessels, generally cylindrical, closed 
at one end, and of different capacities. 

They are employed for small gilding, silvering, and electro- 
plating baths in the cold. They are handy and serviceable for 
amateurs because their transparency permits the progress of the 
operation to be observed at all times. 

Crucibles. — These are vessels, the shape of which is generally 
an inverted truncated cone, Fig. 119, the smaller end being closed, 



APPARATUS AND INSTRUMENTS. 



341 





and the larger open. Sometimes the opening is trian- Fig- lin- 
gular. 

Crucibles are made of many kinds of materials: 
metals, refractory clay, stoneware, porcelain, plum- 
bago, or graphite, etc. They are generally provided 
with a cover of the same material, and are raised above 
the grate bars of the furnace by means of bricks or 
cylinders of clay. Metallic crucibles may be heated rapidly, but 
the others require to have their temperature raised gradually and 
carefully. 

They are employed for the preparation of many salts, for the 
fusion of metals, etc. Non-metallic crucibles are rarely used for 
more than one operation. 

Hydrometers. — These are glass instruments resembling thermo- 
meters in outward appearance, but having a large bulb near the 
bottom. They are used for testing the specific 
gravity of liquids, or, in other words, to test 
their density as compared with that of pure 
water. The liquid to be tested may be placed 
in a narrow glass jar, Fig. 120, together with 
the hydrometer, or may be contained in any 
other vessel. The instrument floats in the liquid 
to be tested, with its bulb below the surface and 
its stem standing above the surface. This stem 
is graded into degrees similar to that of a ther- 
mometer, and shows the depth of the bulb be- 
neath the surface. In pure water the bulb sinks 
down to the 0° mark, or to 1.000 as marked on 
some scales, 1.000 being taken to represent the 
density of water at a temperature of 60° F. As 
the density of water increases by the addition of 
salts or of liquids having a greater density than water, the bulb 
is forced upwards, and the scale then registers so many degrees 
greater density than water. 

Three differently graduated hydrometers are in use, viz : hydro- 
meters graded to read direct the specific gravity of liquids in com- 
parison with that of water, taking this as represented by 1.000; 
hydrometers graded by a scale adopted by Mr. W. Twaddell, and 




342 



ELECTRO-DEPOSITION OF METALS. 



known as Twaddell's hydrometers ; and hydrometers graded by 
a scale adopted by M. Baume, and named Baume's hydrometers. 
The difference between the three gradings is shown in the follow- 
ing table : — 

Table showing readings of different hydrometers. 



Specific gravity. 


Baum§. 


Twaddell. 


Specific gravity. 


Baurae. 


Twaddell. 


.817° 


40° 


_ 


1.250° 




50° 


.827 


38 


— 


1.263 


30° 


— 


.837 


36 


— 


1.300 


— 


60 


.847 


34 


— 


1.321 


35 


— 


.856 


32 


— 


1.350 


— 


70 


.871 


30 


— 


1.385 


40 


— 


.880 


28 


— 


1.400 


— 


80 


.892 


26 


— 


1.450 


— 


90 


.903 


24 


— 


1.454 


45 


— 


.915 


22 


— 


1.500 


— 


100 


.928 


20 


— 


1.532 


50 


— 


.942 


18 


— 


1.550 


— 


110 


.955 


16 


— 


1.600 


— 


120 


.970 


14 


— 


1.618 


55 


— 


.985 


12 


— 


1.650 


— 


130 


1.000 


0° or 10 


0° 


1.700 


— 


140 


1.036 


5 


— 


1.714 


60 


— 


1.050 


— 


10 


1.750 


— 


150 


1.075 


10 


— 


1.800 


— 


160 


1.100 


— 


20 


1.823 


65 


— 


1.116 


15 


— 


1.850 


— 


170 


1.150 


— 


30 


1.900 


— 


180 


1.161 


20 


— 


1.946 


70 


— 


1.200 


— 


40 


1.950 


— 


190 


1.210 


25 


— 









It will be seen that every degree Twaddell represents .005° 
in the specific gravity hydrometer, and every 10° represents 
.050°. To convert degrees Baume into readings showing direct 
specific gravity, subtract the readings on Baume's scale from the 
number 144, and divide this by the difference. For example, 

144 

144 — 66 = -jjTt = 1.846°, the specific gravity of a liquid register- 
ing 66° on a Baume' hydrometer. Baume has one hydrometer 
for liquids lighter than water (the readings of which are given in 
the first 16 sets of figures in the foregoing table), and one for 
liquids heavier than water. 

Filters. — Filtering a solution, a bath, or any other liquor, con- 
sists in causing it to pass through a permeable substance, the pores 



APPARATUS AND INSTRUMENTS. 



343 



Fig. 121. 




or meshes of which are sufficiently close to retain all the undis- 
solved substances, which are thus separated from the liquid part. 

Filters are of very different materials and shapes. Cloth, mus- 
lin, etc., are coarse filters or strainers, made in 
the form of pockets. Their filtering power is 
considerably improved by covering them with a 
layer of sand, wool, bone-black, etc. These 
latter substances themselves, properly supported, 
will act as filters. 

Felted wool (generally rabbit's hair) is made 
in the shape of a conical pocket (Fig. 121), but 
is suited only for neutral substances. Alkalies 
destroy it rapidly. 

Concentrated acids are filtered through amianthus, or asbestos, 
compressed in the neck of a glass funnel upon broken fragments 
of glass. 

The most useful filtering material, however, is unsized paper. 
This filter (Fig. 122), is prepared by folding diago- 
nally a square piece of porous paper, which thus 
prepared forms a triangle. This is again folded in 
half. Then, beginning at one edge, smaller folds 
are made alternately to the right and to the left, 
but all converging towards the point, like a fan. 
The filter is now partially opened, trimmed on top, 
and introduced into the funnel, care being had that all the pro- 
jecting edges rest against it. 

If it be feared that the filter will not resist the weight of the 
liquid, the point is twisted to the left or to the right, and while 
it is still held between two fingers of the left hand, the whole 
filter is inverted, so that the inward folds become 
the outward ones. A filter with such a rounded 
point is better supported in the funnel, and filters 
more rapidly. 

This method is preferable for rapid filtration; but, 
if it is desired to recover precipitates, the filter repre- 
sented by Fig. 123, is more suitable. A circular 
sheet of paper is twice doubled up, and by carefully opening it, 



Fiar. 122. 




Fig. 123. 




344 



ELECTRO-DEPOSITION OF METALS. 



three thicknesses of paper are laid on one side, leaving one single 
thickness on the other side. 

Siphons. — The most simple and handy siphon in many cases, is 
a piece of lead pipe bent so as to have two unequal branches, the 
smaller of which plunges into the liquid to be drawn off. A sec- 
tion of India-rubber tube may be employed for similar purposes. 

But as these materials may be chemically acted upon by various 
solutions, glass siphons are used with or without a suction tube 
(Figs. 124, 125). 



Fig. 124. 



Fig. 125. 





For siphoning corrosive solutions which cannot be touched with 
the fingers, a siphon with a suction tube is used (Fig. 124). The 
shorter leg is plunged into the liquid and the longer one closed 
with the finger or an India-rubber pad passed against it. Then, 
with the mouth, suction should be carefully applied at the lateral 
suction tube until the liquid fills the longer leg. 

If there be danger in inhaling a poisonous vapor, the action of 
the mouth may be replaced by an India-rubber ball fastened to 
the suction tube. The longer branch of the siphon is closed, as 
before, and the ball compressed in order to remove the air. By 
its elasticity the ball resumes its former volume, thus producing 
a suction which starts the siphon in action. 



HYGIENIC RULES FOR THE WORKSHOP. 345 



CHAPTER XVII. 

HYGIENIC RULES FOR THE WORKSHOP. 

In but few other branches of industry has the workman so 
constantly to deal with powerful poisons, as well as other sub- 
stances and vapors, which are exceedingly corrosive in their action 
upon the skin and the mucous membranes, as in electro-plating. 
However, with the necessary care and sobriety, all influences in- 
jurious to health may be readily overcome. 

The necessity of frequently renewing the air in the workshop 
by thorough ventilation has already been referred to in Chapter 
IV., " Electro-plating establishments in general." Workmen 
exclusively engaged in pickling objects are advised to neutralize 
the action of the acids upon the enamel of the teeth and the 
mucous membranes of the mouth and throat by frequently rinsing 
the mouth with dilute solution of bicarbonate of soda. Workmen 
engaged in freeing the objects from grease lose, for want of cleanli- 
ness, the skin on the portions of the fingers which come constantly 
in contact with the lime and caustic lyes. This may be overcome 
by frequently washing the hands in clean water, and previous to 
each intermission in the work, the workman should after washing 
the hands dip them in dilute sulphuric acid, dry them and 
thoroughly rub them with cosmoline or a mixture of equal parts 
of glycerine and water. The use of rubber gloves by workmen 
engaged in freeing the objects from grease cannot be recommended, 
they being expensive and subject to rapid destruction. It is better 
to wrap a linen rag seven or eight times around a sore finger, 
many workmen using this precaution to protect the skin from the 
corrosive action of the lime. 

It should be a rule for every workman employed in an electro- 
plating establishment not to drink from vessels used in electro- 
plating manipulations, for instance, porcelain dishes, beer glasses, 
etc. One workman may this moment use such a vessel to drink 



346 ELECTRO-DEPOSITION OF METALS. 

from and without his knowledge another may employ it the next 
moment for dipping out potassium cyanide solution, and the first 
using it again as a drinking vessel may incur sickness or even fatal 
poisoning. The handling of potassium cyanide and its solutions 
requires constant care and judgment. Working with sore hands 
in such solutions should be avoided as much as possible ; but if 
it has to be done, and the workman feels a sharp pain in the sore, 
wash the latter quickly with clean water and apply a few drops 
of green vitriol solution. Many individuals are very sensitive to 
nickel solutions, eruptions, which are painful and heal slowly, 
breaking out upou the arms and hands, while others may for 
years come in contact with nickel baths without being subject to 
such eruptions. In such case prophylaxis is also the safeguard, 
i. e., to prevent by immediate thorough washing the formation of 
the eruption if the skin has been brought in contact with nickel 
solution, as, for instance, in taking out with the hand an object 
fallen into a nickel bath. 

In the following, some directions will be found for neutralizing, 
in case of internal poisoning, the effects of the poison either en- 
tirely or at least sufficiently to retard its action until professional 
aid can be summoned. 

Poisoning by hydrocyanic (prussic) acid, potassium cyanide, or 
cyanides. — If prussic acid, or the cyanides, be concentrated or have 
been absorbed in considerable quantity, their action is almost 
instantly fatal, and there is little hope of saving the victim, 
although everything should be tried. But if these substances 
have been taken in very dilute condition they may not prove 
immediately fatal, and there is some hope that remedial measures 
may be successfully applied. 

In poisoning, with these substances water as cold as possible 
should be run upon the head and spine of the patient, and he 
should be made to inhale, carefully and moderately, the vapor of 
chlorine water, bleaching powder, or Javelle water (hypochlorite 
of soda). 

Should these poisons be introduced into the stomach there should 
be administered as soon as possible the hydrate of sesquioxide of 
iron, or what is better, dilute solutions of the acetate, citrate, or 



HYGIENIC RULES FOR THE WORKSHOP. 347 

tartrate of iron. "With proper precautions a very dilute solution 
of sulphate of zinc may be given. 

Poisoning by copper-salts. — The stomach should be quickly 
emptied by means of an emetic or in want of this, the patient 
should thrust his finger to the back of his throat and induce 
vomiting by tickling the uvula. After vomiting drink milk, 
white of egg, gum-water or some mucilaginous decoction. 

Poisoning by lead-salts requires the same treatment as poisoning 
by copper-salts. Lemonade of sulphuric acid, or an alkaline solu- 
tion containing carbonic acid, such as Vichy water, or bicarbonate 
of soda, is also very serviceable. 

Poisoning by arsenic. — The stomach must be quickly emptied 
by an energetic emetic, when freshly precipitated ferric hydrate 
and calcined magnesia may be given as an antidote. Calcined 
magnesia being generally on hand, mix it with 15 to 20 times the 
quantity of water and give of this mixture 3 to 6 tablespoonfuls 
every 10 to 15 minutes. 

Poisoning by alkalies. — Use weak acids, such as vinegar, lemon- 
juice, etc., and in their absence, sulphuric, hydrochloric, or nitric 
acid diluted to the strength of lemonade. After the pain in the 
stomach has diminished, it will be well to administer a few spoon- 
fuls of olive oil. 

Poisoning by mercury salts. — Mercury salts, and particularly the 
chloride (corrosive sublimate), form with the white of egg (albumen) 
a compound very insoluble and inert. The remedy is therefore 
indicated. Sulphur and sulphuretted water are also serviceable 
for the purpose. 

Poisoning by sulphuretted hydrogen. — The patient should be 
made to inhale the vapor of chlorine from chlorine water, Javelle 
water or bleaching powder. Energetic friction, especially at the 
extremities of the limbs, should be employed. Large quantities 
of warm and emollient drinks should be given and abundance of 
fresh air. 

Poisoning by chlorine, sulphurous acid, nitrous and hyponitric 
gases. — Admit immediately an abundance of fresh air, and ad- 
minister light inspirations of ammonia. Give plenty of hot drinks 
and excite friction, in order to conserve the warmth and transpira- 
tion of the skin. Employ hot foot-baths to remove the blood from 



348 ELECTRO-DEPOSITION OF METALS. 

the lungs. Afterwards maintain in the mouth of the patient some 
substance which, melting slowly, will keep the throat moist, such 
as jujube and marshmallow paste, molasses candy, and liquorice 
paste. Milk is excellent. 



CHAPTER XVIII. 

CHEMICAL PRODUCTS USED IN THE ELECTRO-PLATING ART. 

In the following the characteristic properties of the chemical 
products employed in the workshop will be briefly discussed, and 
the reactions indicated, which allow of their recognition. It fre- 
quently happens that the labels become detached from the bottles 
and boxes, thus rendering the determination of their contents 
necessary. 

I. Acids. 

1. Sulphuric acid (oil of vitriol). — -Two varieties of this acid 
are found in commerce, viz., fuming sulphuric; acid (disulphuric 
acid), and ordinary sulphuric acid. The first is a thick oily fluid 
generally colored yellowish by organic substances, and emits dense 
white vapors in the air. Its specific gravity is 1.87 to 1.89. The 
only purpose for which fuming sulphuric acid is used in the 
electro-plating art is as a mixture with nitric acid, for stripping 
silvered objects. 

Ordinary sulphuric acid has a specific gravity of 1.84. Diluted 
with water it serves for filling the Bunsen elements and as a pickle 
for iron ; in a concentrated state it is used in the preparation of 
pickles and as an addition to the galvanoplastic copper bath. 
The crude commercial acid generally contains arsenic, hence care 
must be had to procure a pure article. In diluting the acid with 
water, it should in all cases be added to the water in a very gentle 
stream and with constant stirring, as otherwise a sudden genera- 
tion of steam of explosive violence might result, and the danger- 
ously corrosive liquid be scattered in all directions. Concentrated 
sulphuric acid vigorously attacks all organic substances, and hence 



PRODUCTS USED IN ELECTRO-PLATING. 349 

has to be kept in bottles with glass stoppers, and bringing it in 
contact with the skin should be carefully avoided. 

Recognition. — One part of acid mixed with 25 parts of distilled 
water gives, when compounded with a few drops of barium chloride 
solution, a white precipitate of barium sulphate. 

2. Nitric acid {aquafortis, spirit of nitre). — It is found in trade 
of various degrees of strength ; for our purposes acid of 40° 
and 30° Be., being generally used. The acid is usually a more or 
less deep yellow, and frequently contains chlorine. The vapors 
emitted by nitric acid are poisonous and of a characteristic odor 
by which the concentrated acid is readily distinguished from other 
acids. It is used for filling the Bunsen elements, and for pickling 
in combination with sulphuric acid and chlorine. On coming in 
contact with the skin it produces yellow stains. 

Recognition. — By heating the not too dilute acid with copper, 
brown-red vapors are evolved. For the determination of dilute 
nitric acid, add a few drops of it to green vitriol solution, when 
a black-brown coloration will be produced on the point of con- 
tact. 

3. Hydrochloric acid {muriatic acid). — The pure acid is a color- 
less fluid which emits abundant fumes in contact with the air, and 
has a pungent odor by which it is readily distinguished from other 
acids. The specific gravity of the strongest hydrochloric acid is 
1.2 ; the crude acid of commerce has a yellowish color, due to 
iron, and contains arsenic. Dilute hydrochloric acid is used for 
pickling iron and zinc. 

Recognition. — On adding to the acid strongly diluted with 
distilled water a few drops of solution of nitrate of silver in dis- 
tilled water a heavy white precipitate is formed, which becomes 
black by exposure to the light. 

4. Hydrocyanic acid {prussic acid). — This extremely poisonous 
acid exists in nature only in a state of combination in certain 
vegetables and fruits, and especially in the kernels of the latter, 
as, for instance, in the peach, the berries of the cherry laurel, 
bitter almonds, the stones of the apricot, of plums, cherries, etc. 
It may be obtained anhydrous, but in this state it is useless, and 
very difficult to preserve from decomposition. Diluted hydro- 
cyanic acid is colorless with a bitter taste, and the characteristic 



350 ELECTRO-DEPOSITION OF METALS. 

smell of bitter almonds. It is employed in the preparation of 
gold immersing baths, and for the decomposition of the potassa 
in old silver baths. The inhalation of the vapors of this acid 
may have a fatal effect, as also its coming in contact with wounds. 
Recognition. — By its characteristic smell of bitter almonds. Or 
mix it with potash lye until blue litmus paper is no longer red- 
dened, then add solution of green vitriol, which has been partially 
oxidized by standing in the air, and acidulate with hydrochloric 
acid. A precipitate of Berlin blue is formed. 

5. Citric acid. — Clear colorless crystals of 1.542 specific gravity, 
which dissolve with great ease in both hot and cold water. It is 
frequently employed for acidulating nickel baths and, combined 
with sodium citrate, in the preparation of platinum baths. 

Recognition. — Lime-water compounded with aqueous solution 
of citric acid remains clear in the cold, but on boiling deposits a 
precipitate of calcium citrate. This precipitate is soluble in 
ammonium chloride, but on boiling is again precipitated, and is 
then insoluble in sal ammoniac. 

6. Boric acid (boracic acid). — This acid is found in commerce 
in the shape of scales with nacreous lustre and greasy to the 
touch ; when obtained from solutions by evaporation, it forms 
colorless prisms. Its specific gravity is 1.435; it dissolves with 
difficulty in cold water (1 part of acid requiring at 64.4° F., 28 
of water), but is more rapidly soluble in boiling water (1 part of 
acid requiring 3 of water at 212° F.). According to Weston's 
proposition boric acid is employed as an addition to nickel baths, 
etc. 

Recognition. — By mixing solution of boric acid in water with 
some hydrochloric acid and dipping turmeric paper in the solution, 
the latter acquires a brown color, the color becoming more intense 
on drying. Alkalies impart to turmeric paper a similar coloration, 
which, however, disappears on immersing the paper in dilute 
hydrochloric acid. 

7. Arsenious acid (white arsenic, arsenic, ratsbane). — It generally 
occurs in the shape of a white powder and sometimes in vitreous- 
like lumps, resembling porcelain ; for our purposes the white 
powder is almost exclusively used. It is slightly soluble in cold 
water, and more readily in hot water and hydrochloric acid. Not- 



PRODUCTS USED IX ELECTRO-PLATING. 351 

withstanding its greater specific gravity (3.7), only a portion of 
the powder sinks to the bottom on mixing it with water, another 
portion being retained on the surface by air bubbles adhering to 
it. It is employed as an addition to brass baths, further, in the 
preparation of arsenic baths, for blacking copper alloys, and in 
certain silver whitening baths. 

Recognition. — When some arsenious acid is thrown upon glow- 
ing coals an odor resembling that of garlic is perceptible. By 
mixing solution of arsenious acid, prepared by boiling with water, 
with a few drops of ammoniacal solution of nitrate of silver, a 
yellow precipitate of arsenate of silver is obtained. The am- 
moniacal solution of nitrate of silver is prepared by adding 
ammonia to solution of nitrate of silver until the precipitate at 
first formed disappears. 

8. Chromic acid. — It forms crimson-red needles, and also occurs 
in commerce in the shape of red powder. It is readily soluble in 
water forming a red fluid which serves for filling batteries. 

Recognition. — Chromic acid can scarcely be mistaken for any 
other chemical product employed by the electro-plater. A strongly 
diluted solution of it gives, after neutralizing with caustic alkali 
and adding a few drops of nitrate of silver solution, a crimson- 
red precipitate of chromate of silver. 

II. Alkalies and Alkaline Earths. 

9. Potassium hydrate {caustic potash). — It is found in commerce 
in various degrees of purity, either in sticks or cakes. It is very 
deliquescent and dissolves readily in water and alcohol ; by ab- 
sorbing carbonic acid from the air it rapidly becomes converted 
into the carbonate and thus loses its caustic properties. It should, 
therefore, be stored in well-closed vessels. Substances moistened 
with solution of caustic potash give rise to a peculiar soapy 
sensation of the skin when touched. It should never be allowed to 
enter the mouth, as even dilute solutions almost instantaneously re- 
move the lining of tender skin. Should such an accident happen, 
the mouth should be at once several times rinsed with water and 
then with very dilute acetic acid. Pure caustic potash serves as 
an addition to zinc baths, gold baths, etc. For the purpose of 



352 ELECTRO-DEPOSITION OF METALS. 

freeing objects from grease the more impure commercial article is 
used. 

10. Sodium hydrate (caustic soda). — It also occurs in commerce 
in various degrees of purity, either in sticks or lumps. It is of a 
highly caustic character resembling potassium hydrate (see above), 
in properties and effects. It is employed for freeing objects from 
grease. 

1 1 . Ammonium hydrate {ammonia or spirits of hartshorn). — It is 
simply water saturated with ammonia gas. By exposure ammonia 
gas is gradually evolved, so that it must be stored in closely- 
stoppered bottles in order to preserve the strength of the solution 
unimpaired. Four qualities are generally found in commerce, viz., 
ammonia of 0.910 specific gravity (containing 24.2 per cent, of 
ammonia gas); of 0.920 specific gravity (with 21.2 per cent, of 
ammonia gas); of 0.940 specific gravity (with 15.2 per cent, of 
ammonia gas) ; and 0.960 specific gravity (with 9.75 per cent, of 
ammonia gas). It is employed for neutralizing nickel and cobalt 
baths when too acid, in the preparation of fulminating gold, and 
as an addition to some copper and brass baths. 

Recognition. — By the odor. 

12. Calcium hydrate (burnt or quick lime). — It forms hard, 
white to gray, pieces which on moistening with water crumble to 
a light white powder, evolving thereby much heat. Vienna lime 
is burnt lime containing magnesia. Lime serves for freeing ob- 
jects from grease and for this purpose is made into a thinly-fluid 
paste with chalk and water with which the objects to be freed 
from grease are brushed. Vienna lime is much used as a polish- 
ing agent. 

III. Sulphur Combinations. 

13. Sulphuretted hydrogen (sulphydric acid, hydrosulphuric 
acid). — A very poisonous colorless gas with a fetid smell resembling 
that of rotten eggs. Ignited in the air it burns with a blue flame, 
sulphurous acid and water being formed. At the ordinary 
temperature water absorbs about three times its own volume of 
the gas, and then acquires the same properties as the gas itself. 
Sulphuretted hydrogen serves for the metallizing of moulds as 



PRODUCTS USED IN ELECTRO-PLATING. 353 

described on p. 307, where the manner of evolving it is also 
given. It is sometimes employed for the production of " oxidized" 
silver. Bringing not only metallic salts, but gilt or silvered arti- 
cles, or pure gold and silver, in contact with sulphuretted hydro- 
gen, should be carefully avoided, they being rapidly sulphurized 
by it. 

Recognition. — By its penetrating smell ; further, by a strip of 
paper moistened with sugar of lead solution becoming black when 
brought into a solution or an atmosphere containing sulphuretted 
hydrogen. 

14. Potassium sulphide (liver of sulphur). — It forms a hard 
green-yellow to pale brown mass, with conchoidal fracture; it 
readily absorbs moisture, whereby it deliquesces and smells of 
sulphuretted hydrogen. It is employed for coloring copper and 
silver black. 

Recognition. — On pouring an acid over liver of sulphur sulphu- 
retted hydrogen is evolved with effervescence, sulphur being at 
the same time separated. 

15. Ammonium sulphide (sulphydrate or hydrosulphate of am- 
monia). — When freshly prepared it forms a clear and colorless 
fluid, with an odor of ammonia and sulphuretted hydrogen ; by 
standing it becomes yellow and, later on, precipitates sulphur. It 
is used for the same purpose as liver of sulphur. 

16. Carbon disulphide or bisulphide. — Pure carbon disulphide 
is a colorless and transparent liquid, which is very dense, and 
exhibits the property of double refraction. Its smell is charac- 
teristic and most disgusting, and may be compared to that of 
rotten turnips. It burns with the blue flame of sulphurous acid, 
carbonic acid being at the same time produced. It is used as 
a solvent for phosphorus and caoutchouc in metallizing moulds 
according to Parkes's method. This solution should be very care- 
fully handled. 

17. Antimony sulphide, a. Black sulphide of antimony {stibium 
sulfuratum nigrum) is found in commerce in heavy, gray, and 
lustreless pieces or as a fine black -gray powder, with slight lustre. 
It serves for the preparation of antimony baths, and for coloring 
copper alloys black. 

23 



354 ELECTRO-DEPOSITION OF METALS. 

b. Red sulphide of antimony {stibium sulfur atum aurantiacum) 
forms a delicate orange-red powder without taste or odor ; it is 
insoluble in water, but soluble in ammonium sulphide, spirits of 
hartshorn, and alkaline lyes ; in connection with ammonium sul- 
phide or ammonia it serves for coloring brass brown. 

18. Arsenic trisulphide or arsenious sulphide (orpiment).— It is 
found in commerce in the natural as well as artificial state, the 
former occurring mostly in kidney-shaped masses of a lemon 
color, and the latter in more orange-red masses, or as a dull yellow 
powder. Specific gravity 3.46. It is soluble in the alkalies and 
spirits of sal ammoniac. 

19. Ferric sulphide. — Hard black masses, generally in flat plates, 
which are only used for the evolution of sulphuretted hydrogen. 

IV. Chlorine Combinations. 

20. Sodium chloride (common salt, rock salt). — The pure salt 
should form white cubical crystals, of which 100 parts of cold 
water dissolve 36, hot water dissolving slightly more. The 
specific gravity of sodium chloride is 2.2. In electroplating, 
sodium chloride is employed as a conducting salt for some gold 
baths, as a constituent of argentiferous pastes, and for precipita- 
ting the silver as chloride from argentiferous solutions. 

Recognition. — An aqueous solution of sodium chloride on being 
mixed with a few drops of lunar caustic solution yields a white 
caseous precipitate, which becomes black by exposure to light and 
does not disappear by the addition of nitric acid, but is dissolved 
by ammonia in excess. 

21. Ammonium chloride (sal ammoniac). — A white substance 
found in commerce in the shape of tough fibrous crystals. It 
has a sharp saline taste, aud is soluble in 2f parts of cold, and in 
a much smaller quantity, of hot water. By heat it is sublimed 
without decomposition. It serves for soldering and tinning, and 
as a conducting salt for many baths. 

Recognition. — By the sublimation on heating. By adding to a 
saturated solution of the salt a few drops of solution of platinum 
chloride, a yellow precipitate of platoso-ammonium chloride is 
formed. 



PRODUCTS USED IN ELECTRO-PLATING. 355 

22. Antimony trichloride (butter of antimony). — A crystalline 
mass which readily deliquesces in the air. Its solution in hydro- 
chloric acid yields the liquor stibii chlorati, also called liquid butter 
of antimony ; it has a yellowish color, and on mixing with water 
yields an abundant white precipitate soluble in potash lye. The 
solution serves for coloring brass steel-gray, and for browning 
gun-barrels. 

23. Arsenious chloride. — A thick oily fluid, which evaporates 
in the air with the emission of white vapors. 

24. Copper chloride. — Blue green crystals readily soluble in 
water. The concentrated solution is green, and the dilute solu- 
tion blue. On evaporating to dryness, brown-yellow copper 
chloride is formed. It is employed in copper and brass baths as 
well as for patinizing. 

25. Tin chlorides, a. Stannous chloride or tin salt — A white 
crystalline salt readily soluble in water, but its solution on ex- 
posure to the air becomps turbid ; by adding, however, hydro- 
chloric acid, it again becomes clear. On fusing the crystallized 
salt it loses its water of crystallization, and forms a solid non- 
transparent mass of a pale yellow color — the fused tin salt. 

The crystallized, as well as the fused, salt serves for the prepa- 
ration of brass, bronze, and tin baths. 

Recognition. — By pouring hydrochloric acid over a small quan- 
tity of tin salt and adding potassium chromate solution, the solu- 
tion acquires a green color. By mixing dilute tin salt solution 
with some chlorine water and adding a few drops of gold 
chloride solution, purple of Cassius is precipitated ; very dilute 
solutions acquire a purple color. 

b. Stannic chloride occurs in commerce in colorless crystals, and 
in the anhydrous state forms a yellowish, strongly fuming caustic 
liquid known as the " fuming liquor of Libadius." 

26. Zinc chloride (hydrochlorate or muriate of zinc; butter of 
zinc). — A white crystalline or fused mass which is very soluble 
and deliquescent. The salt prepared by evaporation generally 
contains some zinc oxy chloride and hence does not yield an en- 
tirely clear solution. It serves for preparing brass and zinc 
baths, and its solution for nickeling by immersion, soldering, etc. 



356 ELECTRO-DEPOSITION OF METALS. 

Recognition. — Solution of caustic potash separates a voluminous 
precipitate of zinc oxyhydrate which redissolves in an excess of 
the caustic potash solution. By conducting sulphuretted hydrogen 
into a solution of zinc salt acidulated with acetic acid, a precipi- 
tate of white zinc sulphide is formed. 

27. Zinc chloride and ammonium chloride. — This salt is a com- 
bination of zinc chloride with sal ammoniac and forms a white 
very deliquescent powder. Its solution serves for soldering and 
for zincking by contact. 

28. Nickel chloride. — It is found in commerce in the shape of 
deep green crystals and of a pale green powder ; the latter con- 
tains considerably less water and less free acid than the crystallized 
article, and is to be preferred for electro-plating purposes. The 
crystallized salt dissolves readily in water, and the powder some- 
what more slowly ; should the solution of the latter deposit a 
yellow precipitate, consisting of basic nickel chloride, it has to be 
brought into solution by the addition of a small quantity of hy- 
drochloric acid. Nickel chloride is employed for nickel baths. 

Recognition. — By mixing the green solution of the salt with 
some spirits of sal ammoniac, a precipitate is formed which dis- 
solves in an excess of spirits of sal ammoniac, the solution show- 
ing a deep blue color. 

29. Cobalt chloride. — It forms small rose-colored crystals, 
which, on heating, yield their water of crystallization and are 
converted into a blue mass. The crystals are readily soluble in 
water, while the anhydrous blue powder dissolves slowly. Cobalt 
chloride is employed for the preparation of cobalt baths. 

Recognition. — Caustic potash precipitates from a solution of 
cobalt chloride a blue basic salt which is gradually converted into 
a rose-colored hydrate, and, with the access of air, into green- 
brown cobaltous hydrate ; the aqueous solution yields with solu- 
tion of yellow prussiate of potash a pale gray-green precipitate. 

30. Silver chloride (horn silver). — A heavy white powder gradu- 
ally passing, by exposure to white light, through a gradation of 
shades from violet to black. By precipitation from silver solu- 
tions it separates as a caseous precipitate (p. 231). At 500° F. it 
melts, without decomposing, to a yellowish fluid, which, on cool- 
ing, congeals to a transparent, tenacious, horn-like mass. Chloride 



PRODUCTS USED IN ELECTRO-PLATING. 357 

of silver is practically insoluble in water, but dissolves readily in 
spirits of sal ammoniac and in potassium cyanide solution. It is 
employed in the preparation of baths for electro-silvering, for the 
whitening baths, and for the pastes for silvering by friction. 

Recognition. — By its solubility in ammonia, pulverulent metallic 
silver being separated from the solution by dipping in it bright 
ribbands of copper. 

3 1 . Gold chloride (terchloride of gold, muriate of gold, auric 
chloride). — This salt occurs in commerce as crystallized gold 
chloride of an orange-yellow color, and as a brown crystalline 
mass, which is designated as neutral gold chloride, or as gold 
chloride free from acid, whilst the crystallized article always con- 
tains acid, and, hence, should not be used for gold baths. Gold 
chloride absorbs atmospheric moisture and becomes resolved into 
a liquid of a fine gold color. On being moderately heated 
yellowish-white aurous chloride is formed, and on being subjected 
to stronger heat it is decomposed to metallic gold and chlorine 
gas. By mixing its aqueous solution with ammonia, a yellow- 
brown powder consisting of fulminating gold is formed. In a dry 
state this powder is highly explosive, and, hence, when precipi- 
tating it from gold chloride solution for the preparation of gold 
baths, it must be used while still moist. 

Recognition. — By the formation of the precipitate of fulminating 
gold on mixing the gold chloride solution with ammonia. Further 
by the precipitation of brown metallic gold pow T der on mixing 
the gold chloride solution with green vitriol solution. 

32. Platinic chloride. — The substance usually known by this 
name is hydroplatinic chloride. It forms red-brown very soluble 
— and in fact deliquescent — crystals. With ammonium chloride 
it forms platoso-ammonium chloride (see p. 252). Both combina- 
tions are used in the preparation of platinum baths. The solu- 
tion of platinic chloride also serves for coloring silver, tin, brass, 
and other metals. 

Recognition. — By the formation of a precipitate of yellow platoso- 
ammonium chloride by mixing concentrated platinic chloride solu- 
tion with a few drops of saturated sal ammoniac solution. 



358 ELECTRO-DEPOSITION OF METALS. 

V . Cyanides. 

33. Potassium cyanide (white prussiate of potash). — For electro- 
plating purposes pure potassium cyanide with 98 to 99 per cent., 
as well as that containing 80, 70, and 60 per cent., is used, whilst 
For pickling the preparation with 45 per cent, is employed. For 
the preparation of alkaline copper and brass baths, as well as 
silver baths, the pure 98 to 99 per cent, product is generally 
employed. However, for preparing gold baths the 60 per cent, 
article is mostly preferred, because the potash present in all potas- 
sium cyanide varieties with a lower content renders fresh baths 
more conductive. However, gold baths may also be prepared 
with 98 per cent, potassium cyanide without fear of injury to the 
efficiency of the baths, while, under ordinary circumstances, a 
preparation with less than 98 per cent, may safely be used for the 
rest of the baths. However, when potassium cyanide has to be 
added to the baths, as is from time to time necessary, only the 
pure preparation free from potash should be used, because the 
potash contained in the inferior qualities gradually thickens the 
bath too much. 

No product is more important to the electro-plater than potas- 
sium cyanide. The pure 98 to 99 per cent, product is a white 
transparent crystalline mass, the crystalline structure being plainly 
perceptible upon the fracture. In a dry state it is odorless, but 
when it has absorbed some moisture it has a strong smell of prus- 
sic acid. It is readily soluble in water, and should be dissolved 
in cold water only, since when poured into hot water it is partially 
decomposed, which is recognized by the appearance of an odor of 
ammonia. Potassium cyanide solution in cold water may, how- 
ever, be boiled for a short time without suffering essential decom- 
position. Potassium cyanide must be kept in well-closed vessels, 
being when exposed to the air deliquescent, and it is decomposed 
by the carbonic acid of the air, whereby potassium carbonate is 
formed while prussic acid escapes. It is a deadly poison and 
must be used with the utmost caution. Potassium cyanide with 
80, 70, 60, or 45 per cent, forms a gray-white to white mass 
with a porcelain-like fracture. A pale gray coloration is not a 
proof of impurities, it being due to somewhat too high a tern- 



PRODUCTS USED IN ELECTRO-PLATING. 359 

perature in fusing. These varieties are found in commerce in 
irregular lumps or in sticks, the use of the latter offering no 
advantage. Their behavior towards the air and in dissolving is 
the same as that of the pure product. 

Recognition. — By the bitter almond smell of the solution. By 
mixing potassium cyanide solution with ferric-chloride and then 
with hydrochloric acid until the latter strongly predominates, a 
precipitate of Berlin blue is formed. 

The pure salt free from potash does not effervesce on adding 
dilute acid, which is, however, the case with the inferior qualities. 

To facilitate the use of potassium cyanide with a different con- 
tent than that given in a formula for preparing a bath, the fol- 
lowing table is here given : — 



per cent. 



Potassium cyanide with 
80 per cent. 70 per cent. 60 per cent. 45 per cent. 



By weight. By weight. By weight. By weight. By weight. 

1 part = 1.230 parts = 1.400 parts = 1.660 parts = 2.180 parts. 
0.820 " = 1 " = 1.143 " = 1.333 " = 1.780 " 

0.714 " =0.875 " =1 " =1.170 " =1.550 " 

0.615 " =0.750 " =0.857 " = 1 " =1.450 " 

0.460 " =0.562 " =0.643 " =0.750 " =1 " 

34. Copper cyanides. — There is a cuprous and a cupric cyanide ; 
that used for electro-plating purposes being a mixture of both. 
It is a green-brown powder which should not be dried since in 
the moist state it dissolves more readily in potassium cyanide. 
It is only used as a double salt, i. e., in combination with potas- 
sium cyanide in the preparation of copper, brass, tombac, and 
red gold baths. 

Recognition. — By evaporating a piece of copper cyanide the size 
of a pea, or its solution in hydrochloric acid to dryness in a water 
bath, whereon care must be taken not to inhale the vapors, and 
dissolving the residue in water, a green-blue solution is obtained 
which acquires a deep blue color by the addition of ammonia in 
excess. 

35. Zinc cyanide (hydrocyanate of zinc, prussiate of zinc). — A 
white powder insoluble in water, but soluble in potassium cyanide, 
ammonia and the alkaline sulphites ; the fresher it is, the more 



360 ELECTRO-DEPOSITION OF METALS. 

readily it dissolves, the dried product dissolving with difficulty. 
Its solution in potassium cyanide is used for brass baths. 

Recognition. — By evaporating zinc cyanide or its solution in an 
excess of hydrochloric acid, zinc chloride remains behind, which 
is recognized by the reaction given under zinc chloride. 

36. Silver cyanide (prussiate, or hydrocyanate of silver). — A 
white powder which slowly becomes black when exposed to light. 
It is insoluble in water and cold acids which, however, will dis- 
solve it with the aid of heat. At 750° F. it melts to a dark red 
fluid which, on cooling, forms a yellow mass with a granular struc- 
ture. It is readily dissolved by potassium cyanide, but is only 
slightly soluble in ammonia, differing in this respect from silver 
chloride. It forms a double salt with potassium cyanide, and as 
such is employed in the preparation of silver baths. 

37. Potassium ferro-cyanide (yellow prussiate of potash). — It 
occurs in the shape of yellow semi-translucent crystals with 
mother-of-pearl lustre, which break gradually and without noise. 
For the solution of 1 part of it, 4 of water are required, the 
solution exhibiting a pale yellow color. It precipitates nearly all 
the metallic salts from their solutions, some of the precipitates 
being soluble in an excess of the precipitating agent. This salt 
is not poisonous. It serves for the preparation of silver and gold 
baths; its employment, however, offering no advantages over 
potassium cyanide except its non-poisonous properties be con- 
sidered as such. 

Recognition. — When the yellow solution is mixed with ferric 
chloride, a precipitate of Berlin blue is formed. 

VI. Carbonates. 

38. Potassium carbonate (potash). — It is found in commerce in 
gray-white, bluish, yellowish pieces, the colorations being due to 
admixtures of small quantities of various metallic oxides, and pure 
in the form of a white powder or in pieces the size of a pea. 
The salt being very deliquescent has to be kept in well-closed 
receptacles. It is readily soluble, and if pure, the solution in 
distilled water must be clear. It serves as an addition to some 
baths, and in an impure state for freeing objects from grease. 



PRODUCTS USED IN ELECTROPLATING. 361 

Recognition. — The solution effervesces on the addition of hydro- 
chloric acid. The solution neutralized with hydrochloric acid 
gives with platinum chloride a heavy yellow precipitate, provided 
the solution be not too dilute. 

39. Acid potassium carbonate or monopotassic carbonate, com- 
monly called bicarbonate of potash. — Colorless transparent crys- 
tals, which at a medium temperature dissolve to a clear solution 
in 4 parts of water. It is not deliquescent ; however, on boiling 
its solution loses carbonic acid, and contains then only potassium 
carbonate. It is employed for the preparation of certain baths 
for gilding by simple immersion. 

40. Sodium carbonate (washing soda). — It occurs in commerce 
as crystallized or calcined soda of various degrees of purity. 
The crystallized product forms colorless crystals or masses of 
crystals, which on exposure to air rapidly effloresce and crumble 
to a white powder. By glowing, the crystals also lose their water, 
a white powder, the so-called calcined soda, remaining behind. 
Soda dissolves readily in water, and serves as an addition to 
copper and brass baths, for the preparation of metallic carbonates, 
and for freeing objects from grease, the ordinary impure soda 
being used for the latter purpose. 

The directions for additions of sodium carbonate to baths gene- 
rally refer to the crystallized salt. If calcined soda is to be used 
instead, 0.4 part of it will have to be taken for 1 part of the 
crystallized product. 

41. Sodium bicarbonate (baking powder). — A dull w r hite powder 
soluble in 10 parts of water of 68° F. On boiling, the solution 
loses one-half of its carbonic acid, and then contains sodium car- 
bonate only. 

42. Calcium carbonate {marble, chalk). — When pure it forms a 
snow-white crystalline powder, a yellowish color indicating a con- 
tent of iron. It is insoluble in water, but soluble, with effer- 
vescence, in hydrochloric, nitric, and acetic acids. In nature, 
calcium carbonate occurs as marble, limestone, chalk. 

In the form of whiting (ground chalk carefully cleansed from 
all stony matter) it is used for the removal of an excess of acid in 
acid copper baths, and mixed with burnt lime as an agent for free- 
ing objects from grease. 



362 ELECTRO-DEPOSITION OF METALS. 

43. Copper carbonate. — Occurs in nature as malachite and 
allied minerals. The artificial carbonate is an azure-blue sub- 
stance, insoluble in water, but soluble, with effervescence, in 
acids. Copper carbonate precipitated from copper solution by 
alkaline carbonates has a greenish color. 

Copper carbonate is employed for copper and brass baths, and 
for the removal of an excess of acid in acid copper baths. 

Recognition. — Dissolves in acids with effervescence ; on dipping 
a ribband of bright sheet-iron in the solution, copper separates 
upon the iron. On compounding the solution with ammonia in 
excess, a deep blue coloration is obtained. 

44. Zinc carbonate. — A white powder, insoluble in water. The 
product obtained by precipitating a zinc salt with alkaline carbo- 
nates, is a combination of zinc carbonate with zinc oxyhydrate. 

It serves for brass baths in connection with potassium cyanide. 

Recognition. — In a solution in hydrochloric acid, which is 
formed with effervescence, according to the reactions given under 
zinc chloride (26). 

45. Nickel carbonate. — A pale apple green powder, insoluble in 
water, but soluble, with effervescence, in acids. It is employed 
for neutralizing nickel baths which have become acid. 

Recognition. — In hydrochloric acid it dissolves, with efferves- 
cence, to a green fluid ; by the addition of a small quantity of 
ammonia, nickel oxyhydrate is precipitated, which, by adding am- 
monia in excess, is redissolved, the solution showing a blue color. 

46. Cobalt carbonate. — A reddish powder, insoluble in water, 
but soluble in acids, the solution forming a red fluid. 

VII. Sulphates and Sulphites. 

47. Sodium sulphate (Glauber's salt). — Clear crystals of a 
slightly bitter taste, which effloresce by exposure to the air. 
They are readily soluble in water. On heating, the crystals 
melt in their water of crystallization, and on glowing, calcined 
Glauber's salt remains behind. It is used as an addition to some 
baths. 

48. Ammonium sulphate. — It forms a neutral colorless salt, 
which is constant in the air, readily dissolves in water and evapo- 



PRODUCTS USED IN ELECTRO-PLATING. 363 

rates on heating. It serves as a conducting salt for nickel, cobalt, 
and zinc baths. 

Recognition. — By its evaporating on heating ; a concentrated 
solution compounded with platinic chloride gives a yellow precipi- 
tate of platoso-ammonium chloride, while a solution mixed with 
a few drops of hydrochloric acid gives with barium chloride a 
precipitate of barium sulphate. 

49. Aluminium potassium sulphate (potash-alum). — Colorless 
crystals or pieces of crystals with an astringent taste. It is solu- 
ble in water, 12 parts of it dissolving in 100 parts of water at the 
ordinary temperature. On heating the crystals melt and are con- 
verted into a white spongy mass, the so-called burnt alum. 

Potash-alum serves for the preparation of zinc baths and for 
brightening the color of gold. 

Recognition. — On adding sodium phosphate to the solution a 
jelly-like precipitate of aluminium phosphate is formed, which is 
soluble in caustic potash but insoluble in acetic acid. 

50. Ammonium-alum is exactly analogous to the above, the 
potassium sulphate being simply replaced by ammonium sulphate. 
It is for most purposes interchangeable with potash-alum. On 
glowing ammonium-alum the ammonium sulphate is lost, pure 
alumina remaining behind. Ammonium-alum is used for pre- 
paring a bath for zincking iron and steel by immersion. 

Recognition. — The same as potash-alum. On heating the com- 
minuted ammonium-alum with potash lye an odor of ammonia 
becomes perceptible. 

51. Iron sulphate (iron protosulphate, ferrous sulphate or green 
vitriol). — Pure green vitriol forms bluish-green transparent crys- 
tals of a sweetish astringent taste, which readily dissolve in water. 
Crude green vitriol is a green crystalline substance, often yellowish 
on the exterior owing to the formation of ferric compounds with the 
aid of atmospheric oxygen. It generally contains, besides ferrous 
sulphate, the sulphates of copper and zinc as well as ferric sul- 
phate. On account of the tendency to peroxidation green vitriol 
and other ferrous compounds should not be exposed to the air 
any more than is necessary. 

Green vitriol is employed for the preparation of iron baths, and 
for the reduction of gold from its solutions. 



364 ELECTKO-DEPOSITION OF METALS. 

Recognition. — By compounding the green solution with a few 
drops of concentrated nitric acid, a black -blue ring is formed on 
the point of contact. On mixing the lukewarm solution with 
gold chloride, gold is separated as a brown powder, which by rub- 
bing acquires the lustre of gold. 

52. Iron-ammonium sulphate. — Green crystals which are constant 
in the air and do not oxidize as readily as green vitriol. 100 parts 
of water dissolve 16 parts of this salt. It is used for the same 
purposes as green vitriol. 

53. Copper sulphate (cupric sulphate or blue vitriol). — It forms 
blue crystals, of which, 100 parts of cold water, dissolve about 40, 
and the same volume of hot water, about 200 parts. Blue vitriol 
which does not possess a pure blue color, but shows a greenish 
lustre, is contaminated with green vitriol, and should not be used 
for electro-plating purposes. 

Blue vitriol serves for the preparation of alkaline copper and 
brass baths, acid copper baths, etc. 

Recognition. — By its appearance, as it can scarcely be mistaken 
for anything else. A content of iron is recognized by boiling blue 
vitriol solution with a small quantity of nitric acid, and adding 
spirits of sal ammoniac in excess ; brown flakes indicate iron. 

54. Zinc sulphate {white vitriol). — It forms small colorless prisms 
of a harsh metallic taste, which readily oxidize on exposure to the 
air. By heating the crystals melt, and by glowing are decomposed 
to sulphurous acid and oxygen which escape, while zinc oxide 
remains behind as residue. 100 parts of water dissolve about 50 
parts of zinc sulphate in the cold, and nearly 100, at the boiling 
point. Zinc sulphate is employed for the preparation of brass 
and zinc baths. 

Recognition. — By mixing zinc sulphate solution with acetic acid 
and conducting sulphuretted hydrogen into the mixture, a white 
precipitate of zinc sulphide is formed. A slight content of iron 
is recognized by the zinc sulphate solution made alkaline by ammo- 
nia, giving with ammonium sulphide a somewhat colored precipi- 
tate instead of a pure white one. However, a slight content of 
iron does no harm. 

55. Nickel sulphate. — Beautiful dark green crystals, readily 
soluble in water, the solution exhibiting a green color. On heat- 



PRODUCTS USED IN ELECTRO-PLATING. 365 

ing the crystals to above 536° F., yellow anhydrous nickel sul- 
phate remains behind. 

Like the double salt described below it serves for the prepara- 
tion of nickel baths and for coloring zinc. 

Recognition. — By compounding the solution with ammonia the 
green color passes into blue. Potassium carbonate precipitates 
pale green basic nickel carbonate which dissolves on adding am- 
monia in excess, the solution showing a blue color. A content of 
copper is recognized by the separation of black-brown copper sul- 
phide on introducing sulphuretted hydrogen into the heated solu- 
tion previously strongly acidulated with hydrochloric acid. 

56. Nickel ammonium sulphate. — It forms green crystals of a 
somewhat paler color than nickel sulphate. This salt dissolves 
with more difficulty than the preceding, 100 parts of water dis- 
solving only 5.5 parts of it. It is used for the same purposes as 
the nickel sulphate, and also recognized in the same manner. 

57. Cobalt sulphate. — Crimson crystals of a sharp metallic taste, 
which are constant in the air and readily dissolve in water, the 
solution showing a red color. By heating, the crystals lose their 
water of crystallization without, however, melting, and become 
thereby transparent and rose-color. The salt is used for cobalt 
baths for electro-cobalting and cobalting by contact. 

Recognition. — In the presence of ammoniacal salts, caustic pot- 
ash precipitates a blue basic salt which, on heating, changes to a 
rose-colored hydrate, and by standing for some time in the air, to 
a green- brown hydrate. By mixing a concentrated solution of 
the salt strongly acidulated with hydrochloric acid with solution 
of potassium nitrate, a reddish-yellow precipitate is formed. 

58. Cobalt-ammonium sulphate. — This salt forms crystals of the 
same color as cobalt sulphate, which, however, dissolve more 
readily in water. 

59. Sodium sulphite and bisulphite, a. Sodium sulphite. — Clear, 
colorless, and odorless crystals, which are rapidly transformed 
into an amorphous powder by efflorescence. The salt readily 
dissolves in water, the solution showing a slight alkaline reaction 
due to a small content of sodium carbonate. It is employed in 
the preparation of gold, brass, and copper baths, for silvering by 
immersion, etc. 



366 ELECTRO-DEPOSITION OF METALS. 

Recognition. — The solution when mixed with dilute sulphuric 
acid has an odor of burning sulphur. 

b. Sodium bisulphite. — Small crystals or more frequently in the 
shape of a pale yellow powder, with a strong odor of sulphurous 
acid and readily soluble in water. The solution shows a strong 
acid reaction and loses sulphurous acid in the air. It is employed 
in the preparation of alkaline copper and brass baths. 

Both the sulphite and bisulphite must be kept in well closed 
receptacles, as by the absorption of atmospheric oxygen they are 
converted to sulphate. 

VIII. Nitrates. 

60. Potassium nitrate {saltpetre, nitre). — It forms large prismatic 
crystals, generally hollow, but also occurs in commerce in the 
form of a coarse powder, soluble in 4 parts of water at a medium 
temperature. The solution has a bitter saline taste and shows a 
neutral reaction. Potassium nitrate melts at a glowing heat, and, 
on cooling, congeals to an opaque crystalline mass. It is em- 
ployed in the preparation of desilvering baths, for producing a 
dead lustre upon gold and gilding. For these purposes it may, 
however, be replaced by the cheaper sodium nitrate sometimes 
called cubic nitre or Chile saltpetre. 

Recognition. — A small piece of coal when thrown upon melting 
saltpetre burns fiercely. When a not too dilute solution of salt- 
petre is compounded with solution of potassium bitartrate satu- 
rated at the ordinary temperature, a crystalline precipitate of 
tartar is formed. 

61. Sodium nitrate (cubic nitre or Chile saltpetre). — Colorless 
crystals, deliquescent and very soluble in water; the solution 
shows a neutral reaction. It is used for the same purposes as 
potassium nitrate. 

62. Mercurous nitrate. — It forms small colorless crystals which 
are quite transparent and slightly effloresce in the air. On 
heating they melt and are transformed, with the evolution of 
yellow-red vapors, into yellow-red mercuric oxide, which, on 
further heating, entirely evaporates. With a small quantity of 
water mercurous nitrate yields a clear solution, by the further 



PRODUCTS USED IN ELECTRO-PLATING. 367 

addition of water it shows a milky turbidity which, however, 
disappears on adding nitric acid. 

It is employed for quicking the zincs of the elements, and the 
objects previous to silvering, and for brightening gilding. For 
the same purposes is also used : — 

63. Mercuric nitrate. — It is difficult to obtain this salt in a 
crystallized form. It is generally sold in the form of an oily, 
colorless liquid, which, in contact with water, separates a basic 
salt. This precipitate disappears upon the addition of a few drops 
of nitric acid and the liquid becomes clear. 

Recognition. — A bright ribband of copper dipped in solution 
of mercurous or mercuric nitrate becomes coated with a white 
amalgam which disappears upon heating. 

64. Silver nitrate (lunar caustic). — This salt is found in commerce 
in three forms : either as crystallized nitrate of silver in thin, 
rhombic, and transparent plates ; or in amorphous, opaque, and 
white plates of fused nitrate ; or in small cylinders of white, or 
gray or black color according to the nature of the mould em- 
ployed, in which form it constitutes the lunar caustic for surgical 
uses. For our purposes only the pure crystallized product free 
from acid should be employed. The crystals dissolve readily in 
water. In making solutions of this and other silver salts only 
distilled water should be used ; all other waters, owing to the 
presence of chlorine, produce a cloudiness or even a distinct pre- 
cipitate of silver chloride. In the heat the crystals melt to a color- 
less oily fluid, which, on cooling, congeals to a crystalline mass. 

Silver nitrate is employed in the preparation of chloride and 
cyanide of silver for silver baths ; the solution in potassium 
cyanide may also be used for silver baths. The alcoholic solu- 
tion is employed for metallizing moulds. 

Recognition. — Hydrochloric acid and common salt solution pre- 
cipitate from silver nitrate solution silver chloride, which becomes 
black on exposure to the light, and is soluble in ammonia. 

IX. Phosphates and Pyrophosphates. 

65. Sodium phosphate. — Large clear crystals which readily efflo- 
resce, and whose solution in water shows an alkaline reaction. It 



368 ELECTRO-DEPOSITION OF METALS. 

is employed in the preparation of gold baths and for the produc- 
tion of metallic phosphates for soldering. 

Recognition. — The dilute solution compounded with silver 
nitrate yields a yellow precipitate of silver phosphate. 

QQ. Sodium pyrophosphate. — It forms white crystals, which are 
not subject to efflorescence, and are soluble in 6 parts of water at 
a medium temperature ; the solution shows an alkaline reaction. 
Sodium pyrophosphate also occurs in commerce in the form of an 
anhydrous white powder, though it may here be said that the 
directions for preparing baths refer to the crystallized salt. It is 
employed in the preparation of gold, nickel-bronze, and tin baths. 

Recognition. — The dilute solution compounded with silver 
nitrate yields a white instead of a yellow precipitate. 

67. Ammonium phosphate. — A colorless crystalline powder quite 
readily soluble in water ; the solution should be as neutral as pos- 
sible. A salt smelling of ammonia, as well as one showing an 
acid reaction, should be rejected. It is employed in the prepara- 
tion of platinum baths. 

X. Salts of the Organic Acids. 

68. Potassium bitartrate {cream of tartar). — The pure salt forms 
small transparent crystals of an acid taste, and slightly soluble in 
water. The commercial crude tartar or argol, which is a by-pro- 
duct in the wine industry, forms gray or dirty red crystalline 
crusts. In a finely powdered state, purified tartar is called cream 
of tartar. It is employed for the preparation of the whitening 
silver baths, for those of tin, and for the silvering paste by friction. 

69. Potassium sodium tartrate (Rochelle or Seignette salt). — 
Clear colorless crystals, constant in the air, of a cooling bitter 
saline taste, and soluble in 2.5 parts of water of a medium tem- 
perature. The solution shows a neutral reaction. This salt is 
employed in the preparation of copper baths free from cyanide, 
as well as of nickel and cobalt baths, which are to be decomposed 
in the single cell apparatus. 

Recognition. — By the addition of acetic acid the solution yields 
an abundant precipitate of tartar. 



PRODUCTS USED IN ELECTRO-PLATING. 369 

70. Antimony potassium tartrate (tariar emetic). — A white crys- 
talline substance, of which 100 parts of cold water dissolve 5 
parts, while a like volume of hot water dissolves 50 parts. The 
solution shows a slightly acid reaction. The only use of this salt 
is for the preparation of antimony baths. 

Recognition. — The solution compounded with sulphuric, nitric 
or oxalic acid yields a white precipitate, insoluble in an excess of 
the cold acid. Sulphuretted hydrogen imparts to the dilute solu- 
tion a red color. Hydrochloric acid effects a precipitate, which 
is redissolved by the acid in excess. 

71. Copper acetate ((verdigris). — It is found in the market in 
the form of dark green crystals showing an acid reaction, or of a 
neutral bright green powder. 

The crystallized copper acetate forms opaque dark green prisms, 
which readily effloresce, becoming thereby coated with a pale green 
powder ; they dissolve with difficulty in water, but readily in am- 
monia, forming a solution of a blue color, as well as in potassium 
cyanide and alkaline sulphites. 

The neutral copper acetate forms a blue-green crystalline pow- 
der, imperfectly soluble in water, but readily soluble in ammo- 
nia, forming a solution of a blue color. 

Copper acetate is used for preparing copper and brass baths, 
for the production of artificial patinas, for coloring gilding, etc. 

72. Lead acetate (sugar of lead). — Colorless lustrous prisms or 
needles of a nauseous sweet taste and poisonous. The crystals 
effloresce in the air, melt at 104° F., and are readily soluble in 
water, yielding a slightly turbid solution. Lead acetate is em- 
ployed for preparing lead baths (JSTobili's rings) and for coloring 
copper and brass. 

Recognition. — By compounding lead acetate solution with potas- 
sium chromate solution, a heavy yellow precipitate of lead chro- 
mate is formed. 

73. Sodium citrate. — Colorless crystals, presenting a moist ap- 
pearance, which are readily soluble in water ; the solution should 
show a neutral reaction. This salt is employed in the preparation 
of the platinum bath according to Bottger's formula. 

24 



370 



ELECTRO-DEPOSITION OF METALS. 



CHAPTER XIX. 



USEFUL TABLES. 



Table of elements with their symbols, atomic weights, and 
specific gravities. 



[Name 


Sym- 


Atomic 


Specific 


NftlDP 


Sym- 


Atomic 


Specific 




bol. 


weight. 


gravity. 




bol. 


weight. 


gravity. 


Aluminium 


Al 


27.4 


2.67 


Molybdenum 


Mo 


96 


8.60 


Antimony . . 


Sb 


122 


6.72 


Nickel . . 


Ni 


58 


8.8 


Arsenic 


As 


75 


5.63 


Niobium . . 


Nb 


94 


6.67 


Barium . . 


Ba 


137 


4.00 


Nitrogen . 


N 


14 


0.972 


Beryllium . . 


Be 


9.3 


2.10 


Osmium . 


Os 


199.4 


21.3 


Bismuth . . 


Bi 


208 


9.799 


Oxygen . . 


O 


16 


1.088 


Boron . . . 


B 


11 


2.68 


Palladium 


Pd 


106.6 


11.8 


Bromine . . 


Br 


80 


2.97 


Phosphorus . 


P 


31 


1.84 


Cadmium . . 


Cd 


112 


8.67 


Platinum . . 


Pt 


197.4 


21.15 


Caesium . . 


Cs 


133 


— 


Potassium 


K 


39.1 


8.865 


Calcium . . 


Ca 


40 


3.10 


Rhodium . . 


Rh 


104.4 


12.10 


Carbon . . 


C 


12 


3.50 


Rubidium 


Rb 


85.4 


1.50 


Cerium . . 


Ce 


92 


— 


Ruthenium . 


Ru 


104.4 


11.40 


Chlorine . . 


CI 


35.5 


2.45 


Selenium . . 


Se 


79.4 


4.28 


Chromium 


Cr 


52 


6.81 


Silicium . 


Si 


28 


2.49 


Cobalt . . . 


Co 


58.8 


8.50 


Silver . . . 


Ag 


108 


10.50 


Copper . . . 


Cu 


63.4 


8.88 


Sodium . . 


Na 


23 


0.972 


Didymium 


D 


95 


— 


Strontium 


Sr 


87.5 


2.54 


Erbium . . 


E 


112.6 


— 


Sulphur . 


S 


32 


2.045 


Fluorine . . 


F 


19 


— 


Tantalum 


Ta 


182 


10.78 


Gold . . . 


Au 


197 


19.50 


Tellurium 


Te 


128 


6.18 


Hydrogen . . 


H 


1 


0.069 


Thallium . . 


Tl 


204 


11.86 


Indium . . 


In 


75.6 


— 


Thorinum 


Th 


231 


7.70 


Iodine . . . 


I 


127 


4.98 


Tin. . . . 


Sn 


118 


7.29 


Iridium . . 


Ir 


197.4 


21.15 


Titanium 


Ti 


50 


5.30 


Iron . . . 


Fe 


56 


7.70 


Tungsten 


W 


184 


19.10 


Lanthanum . 


La 


92 


— 


Uranium . . 


u 


120 


18.40 


Lead . . . 


Pb 


207 


11.38 


Vanadium 


V 


51.3 


5.50 


Lithium 


Li 


.7 


0.59 


Yttrium . 


Y 


68 


— 


Magnesium 


Mg 


24 


1.74 


Zinc . . . 


Zn 


65 


6.86 


Manganese 


Mn 


55 


8.00 


Zirconium 


Zr 


89.6 


4.20 


Mercury . . 


Hg 


200 


13.59 











USEFUL TABLES. 



371 



Table of chemical and electro-chemical equivalents. 













"Weights 








Chemical 


Electro- 


decomposed 


Name of substance. 


Symbol. 


Specific 


equiva- 


chemical equi- 


by 1 ampere 






gravity. 


lent. 


valent. 
Milligrammes. 


in 1 hour. 
In grammes. 


Hydrogen . 


H 


1 


1 


0.01036 


0.0375 


Aluminium 






Al 


2.6 


13.7 


0.14250 


0.5137 


Antimony . 






Sb 


6.8 


122 


1.26880 


4.5750 


Arsenic 








As 


5.7 


75 


0.78000 


2.8125 


Cobalt 








Co 


8.7 


29.5 


0.30680 


1.1062 


Copper 








Cu 


8.8 


31.8 


0.33070 


1.1925 


Gold . 








Au 


19.2 


98.3 


1.02230 


3.6862 


Iron . 








Fe 


7.5 


28 


0.29120 


1.0500 


Lead . 








Pb 


11.3 


103.5 


1.07640 


3.8812 


Nickel 








Ni 


S.6 


29.5 


0.30680 


1.1062 


Platinum 








Pt 


21.2 


98.6 


1.02540 


3.6975 


Silver 








Ag 


10.5 


108 


1.12320 


4.0500 


Tin . 








Sn 


7.3 


32.7 


0.34010 


1.2262 


Zinc . 








Zn 


7.2 


59 


0.61360 


2.2125 



With the assistance of this table it can be calculated how long 
a measured surface has to remain in the bath in order to acquire 
a deposit of determined weight with the most suitable current-den- 
sity. Suppose the time is to be determined which a square deci- 
meter of surface has to remain in the nickel bath in order to acquire 
a deposit ^ millimetre thick with a current-density of 0.5 ampere. 
First calculate the weight of the deposit by multiplying the surface 
in square millimetres with the thickness and specific gravity. One 
square decimetre is equal to 10,000 square millimetres, which, 
multiplied by y 1 ^- millimetre, gives as a product 1000, which, 
multiplied by the specific gravity of nickel — 8.6, gives 8,600 
milligrammes =8.6 grammes. Since, for the regular deposit per 
square decimeter, a current-density of 0.5 ampere is required, and 
1 ampere deposits, according to the above table, 1.1062 grammes 
in 1 hour, J ampere deposits 0.5331 grammes in 1 hour, and, 
therefore, about 16 hours will be required for the deposition of 
8.6 grammes. 

According to this example the time, for instance, can also be 
calculated, which one, two, or more dozens of knives and forks or 
spoons, which are to have a deposit of silver of a determined weight, 
must remain in the bath when the current-density is known. Sup- 
pose 50 grammes of silver are to be deposited upon 1 dozen of 



372 



ELECTRO-DEPOSITION OF METALS. 



spoons, and the most suitable current-density is 0.2 ampere per 
square decimetre ; if the surface of 1 spoon represents 1.10 square 
decimetres the surface of 1 dozen spoons of equal size is 13.2 
square decimetres. Hence, they require 13.2 X 0.2 = 2.64 am- 
peres ; now, since 1 ampere deposits in one hour 4.05 grammes of 
silver, 2.64 amperes deposit in the same time 10.7 grammes of 
silver, and with this current the dozen spoons must remain about 
4j hours in the bath for the deposition of 50 grammes of silver 
upon this surface. 

Table showing the value of equal current volumes as expressed in 
amperes per square decimetre, per square foot and per square 
inch of electrode surface. 



is 

K> 02 g 

a & <o 


02 CD 

■r- Zi 

&^ 

II 


03 4> 

&* . 

„p,S 


|2 

g-n'3 

g a> <o 


02 a> 

a«°^ 

„a,-2 


02 0> - 

&^ . 

a ** 


£© 

^ CTCl 
/0> 09 2 

fi 04) 
4j »* 


8§ 

u a 

a m +* 
ii 


= Amperes 
per square 
inch. 


0.05 


0.46 


0.0032 


0.8 


7.43 


0.0516 


6.20 


57.6 


0.4 


0.054 


0.5 


0.0035 


0.86 


8 


0.0555 


6.46 


60 


0.4167 


0.077 


0.72 


0.005 


0.9 


8.36 


0.0581 


7 


65.0 


0.4516 


0.1 


0.93 


0.0064 


0.93 


8.64 


0.06 


7.53 


70 


0.4861 


0.11 


1 


0.0069 


0.97 


9 


0.0625 


7.75 


72.0 


0.5 


0.15 


1.44 


0.01 


1 


9.29 


0.0645 


8 


74.3 


0.5161 


0.2 


1.86 


0.0129 


1.08 


10 


0.0694 


8.61 


80 


0.5555 


0.22 


2 


0.0139 


1.09 


10.08 


0.07 


9 


83.6 


0.5806 


0.3 


2.79 


0.0193 


1.24 


11.52 


0.08 


9.30 


86.4 


0.6 


0.31 


2.88 


0.02 


1.39 


12.96 


0.09 


9.69 


90 


0.6250 


0.32 


3 


0.0208 


1.55 


14.4 


0.1 


10 


92.9 


0.6452 


0.4 


3.71 


0.0258 


2 


18.6 


0.1290 


10.76 


100 


0.6944 


0.43 


4 


0.0278 


2.15 


20 


0.1389 


10.85 


100.8 


0.7 


0.46 


4.32 


0.03 


3 


27.9 


0.1935 


12.40 


115.2 


0.8 


0.5 


4.64 


0.0323 


3.10 


28.8 


0.2 


13.95 


129.6 


0.9 


0.54 


5 ' 


0.0348 


3.23 


30 


0.2083 


15.50 


144.0 


1 


0.6 


5.57 


0.0387 


4 


37.1 


0.2581 


20 


185.8 


1.2903 


0.62 


5.76 


0.04 


4.30 


40 


0.2778 


21.53 


200 


1.38S9 


0.65 


6 


0.0417 


4.60 


43.2 


0.3 


30 


278.7 


1.9355 


0.7 


6.50 


0.0452 


5 


46.4 


0.3226 


31.0 


288 


2 


0.75 


7 


0.0486 


5.38 


50 


0.3478 


32.3 


300 


2.0833 


0.77 


7.20 


0.05 


6 


55.7 


0.3871 


46.5 


432.0 


3 



By this table the current-density may be expressed in amperes 
per square decimetre, square foot, or square inch, any of them 
being given. Thus a current of 1 ampere per square decimetre 
has the same electrolytic value as one of 9.29 amperes per square 
foot or 0.0645 per square inch. To find the value of intermediate 



USEFUL TABLES. 



373 



numbers, not shown above, add together the various numbers re- 
presenting the hundreds, tens, units, and decimals of the given 
quantity. Thus 27.5 amperes per square decimetre (= 20 4- 7 4- 5) 
is equivalent to 185.84-654-4.64=255.44 amperes per square 
foot, or 1.29034-0.45164-0.0323=1.7742 amperes per square 
inch. 

Table showing the specific electrical resistances* of different 
sulphuric acid solutions at various temperatures {Fleeming 
Jenkiri). 



Specific 


Temperatures (Fahrenheit). 


gravity of 
acid. 


32° 


39.2° 


46.4° 


53.6° 


60.8° 


68° 


75.2° 


82.4° 


1.10 


1.37 


1.17 


1.04 


0.92 


0.84 


0.79 


0.74 


0.71 


1.20 


1.33 


1.11 


0.93 


0.79 


0.67 


0.57 


0.49 


0.41 


1.25 


1.31 


1.09 


0.90 


0.74 


0.62 


0.51 


0.43 


0.36 


1.30 


1.36 


1.13 


0.94 


0.79 


0.66 


0.56 


0.47 


0.39 


1.40 


1.69 


1.47 


1.30 


1.16 


1.05 


0.96 


0.89 


0.84 


1.50 


2.74 


2.41 


2.13 


1.89 


1.72 


1.61 


1.32 


1.43 


1.60 


4.32 


4.16 


3.62 


3.11 


2.75 


2.46 


2.21 


2.02 


1.70 


9.41 


7.67 


6.25 


5.12 


4.23 


3.57 


3.07 


2.71 



Table showing the specific electrical resistances* of different copper 
sulphate solutions at various temperatures {Fleeming Jenkin). 



No. of parts of 
copper sulphate 
dissolved in 100 
parts of water. 


Temperatures (Fahrenheit). 


57.2° 


60.8° 


64.4° 


68° 


75.2° 


82.4° 


86° 


8 


45.7 


43.7 


41.9 


40.2 


37.1 


34.2 


32.9 


12 


36.3 


34.9 


33.5 


32.2 


29.9 


27.9 


27.0 


16 


31.2 


30.0 


28.9 


27.9 


26.1 


24.6 


24.0 


20 


28.5 


27.5 


26.5 


25.6 


24.1 


22.7 


22.2 


24 


26.9 


25.9 


24.8 


23.9 


22.2 


20.7 


20.0 


28 


24.7 


23.4 


22.1 


21.0 


18.8 


16.9 


16.0 



* By the term " specific resistance," in the above tables, is meant the abso- 
lute resistance in ohms of a column of the liquid 1 square centimetre in cross 
section and 1 centimetre long ; in other words, it is the resistance of a cubic 
centimetre of the liquid. The diminution of resistance accompanying a rise 
of temperature should be especially marked. 



374 



ELECTKODEPOSITION OF METALS. 



Table of the electro- motive force of elements. 



Name of element. 


Constitution. 


Electro- 
motive force 
in volts. 


Authority. 


Wollaston . . 


Amalgamated zinc and cop- 
per in dilute sulphuric 
acid (1 : 12). 


f 0.886 
\ 0.861 
( 0.719 


Clark and Sabine. 

Sprague. 

De la Rive. 


Smee . . . 


Amalgamated zinc in sul- 
phuric acid ; platinized 
silver, or platinum in sul- 
phuric acid (1 : 12). 


f 1.098 
J 1.107 
1 0.541 
[ 1.192 


Clark and Sabine. 
Sprague. 
De la Rive. 
Naclari. 


Daniel! - . 


Amalgamated zinc in sul- 
phuric acid (1 : 4) ; cop- 
per in saturated solution 
of copper sulphate. 


f 1.079 

do. 
1 do. 
L do. 


Clark and Sabine. 
Sprague. 
De la Rive. 
Naclari. 


do. . . . 


Zinc in dilute sulphuric acid 
(1 : 12) ; copper as above. 


f 0.978 
\ 0.98 


Clark and Sabine. 
Du Moncel. 


Leclanche . 


Zinc in sal ammoniac, carbon 
with manganese peroxide 
in sal ammoniac. 


f 1.481 
J 1.561 
1 1.942 
! 1.259 


Clark and Sabine. 
Sprague. 
De la Rive. 
Beetz. 


do. . . . 


Zinc in solution of common 
salt ; carbon with manga- 
nese peroxide in common 
salt solution. 


( 1.493 

\ 1.360 
{ 1.34 


Sprague. 
Naclari. 
Du Moncel. 


Marie Davy 


Zinc in dilute sulphuric acid 
(1 : 12) ; carbon in mercu- 
rous sulphate. 


f 1.524 
J 1.542 
] 1.482 
[ 1.440 


Clark and Sabine. 
Sprague. 
Naclari. 
Du Moncel. 


Grove . . . 


Zinc in dilute sulphuric acid 
(1 : 12) ; platinum in fum- 
ing nitric acid. 


1.956 


Clark and Sabine. 


do. . . . 


Zinc as above ; platinum in 
nitric acid of 1.38 sp. gr. 


/ 1.524 
t 1.542 


Clark and Sabine. 
Sprague. 


Bunsen . . 


Zinc as above ; carbon in 
fuming nitric acid. 


f 1.964 
\ 1.95 


Clark and Sabine. 
Du Moncel. 


do. . . . 


Zinc as above ; carbon in 
nitric acid of 1.38 sp. gr. 


f 1.888 
\ 1.941 
1 ].880 


Clark and Sabine. 

Beetz. 

Naclari. 


do. . . . 


Zinc as above ; carbon in bi- 
chromate of potassium. 


f 2.028 
\ 1.905 
1 2.120 


Clark and Sabine. 

Sprague. 

Naclari. 


Grenet . . . 


Zinc and carbon in bichro- 
mate of potassium. 


1.825 


Naclari. 



USEFUL TABLES. 



375 



Table showing the solubility of various substances. 



Substances of which 1 part is soluble 



Alum .... 

Ammonium carbonate 

Citric acid 

Copper sulphate (blue vitriol) 

Ferric chloride 

Ferrous chloride 

Ferrous sulphate (green vitriol) 

Iodine 

Nickel nitrate . 

" sulphate 
Potash 

" caustic 
Potassium cyanide 

" dichromate (red chro 

mate of potash) 
Sal ammoniac 

Silver, citrate 

" nitrate 

Soda 

" caustic 
Sodium bisulphite . 
" chloride 
" sulphite 
Yellow prussiate of potash 
Zinc chloride . 
" sulphate . 



of 59° F. 



6.5 

4.0 

0.75 

5.0 

0.6 

0.8 

1.5 

7000 

2.0 
3.0 
0.9 
0.5 
readily 
soluble 

10 
3.0 

sparingly 

soluble 

0.8 

1.0 

2.0 
soluble 
2.8 
4.0 
4.0 
0.3 
2.0 



of 212° F. 



0.3 
decomposes 

0.6 

1.3 
very soluble 

<< 

0.3 
soluble 

very soluble 

2.0 
very soluble 

readily 
soluble 

1.2 
1.4 

sparingly 
soluble 
very soluble 

0.3 

0.5 
soluble 

2.5 

1.0 

1.0 
very soluble 

1.0 



in alcohol of 
59° F. 



insoluble, 
soluble. 

insoluble, 
soluble. 

c< 

insoluble, 
readily 

soluble, 
soluble, 
insoluble, 
insoluble, 
soluble, 
soluble. 



insoluble. 

sparingly 

soluble. 



1 part at a 

boiling heat, 
insoluble, 
insoluble. 

60 
insoluble, 
insoluble. 

1 
insoluble. 



Table Showing the Composition of the Most Usual Alloys and 

Solders. 

Alloys are combinations or mixtures, effected by the fusion of 
two or more different metals in definite proportions. The electro- 
plater employs them so constantly that it is important that he be 
acquainted with the compositions of the most usual alloys, and 
that he learn the preparation of several of them, which, like the 
fusible alloys of Darcet, will often be serviceable. 

It is, of course, possible to vary ad infinitum the mixtures and 
the proportions of the component metals given in the following 



376 



ELECTRO-DEPOSITION OF METALS. 



table, and thus to arrive at an unlimited number of alloys which 
on account of slight differences of color, ductility, sonorousness, 
etc., have received a great variety of names.* 



1. Alloys. 







S3 

ft 
ft 

6 


6 

a 

N 




3 


"o 

1 

2 


a 


a 
o 

a 

< 


'3 

CD 


a 
o 
u 




Parts. 


Argentan, elastic . 
Brass for articles worked with 
the hammer 

" for turning . 

" for decorating purposes 

" for sheet 

Britannia 
<( 

Bronze for bells 

" for larger bells . 

" for smaller bells 

" for clocks . 

" for cymbals 

" for gongs . 

" for medals . 

" for large ordnance 

" for small ordnance 

" for statues . 

(< (< 

i< << 
Chrysochalk . 
Darcet's fusible alloy 

a a a 
a a a 

German silver 

a a 
a a 
a a 
it a 

Potin (French yellow brass) 

Similor .... 

Talmi gold 

Telescope mirrors (reflectors) 

Tombac 

" pale . 

" red . 

" resembling gold 




57.4 

70 

66 

60 

75 
4 

10 

80 

78 

42 

75 

80 
100 
100 

90 

93 

84 

84 

82 

80 

50 

53 
8 
4 

55 

11.9 
100 

86.6 
100 

80 

76 

88 

84 


25 

30 
32 
40 

25 

6 

11 
10.5 

3.5 

31.25 
3.5 
1 

17 
24.9 
12 
12.6 

20 
24 
12 
16 


70.5 
22 
20 
22 
58 
25 
20 
25 

8 
10 

7 
16 

4 
18 

8 

4 

3 

2 

2 
1.2 

2.4 

50 


2 

1 

4 
5 
3 

0.2 
1.2 


13 

4 

15.75 

3 

1 

23 


8 
8 
5 


25.5 
62 


1 


9 
3 



* For a full description of alloys and amalgams see " The Metallic Alloys,' 
edited by W. T. Brannt. Philadelphia : Henry Carey Baird & Co. 1889. 



USEFUL TABLES. 



377 



2. Solders. 
a. Soft Solder. 



Tin. 


Lead. 


Melts 


Tin. 


Lead. 


Melts 






at degrees F. 




at degrees F. 


Parts. 




Parts. 






25 


558° 


H 




334° 




10 


541 


2 




340 




5 


511 


3 




356 




3 


482 


4 




365 




2 


441 


5 




378 




1 


370 


6 




381 



b. Hard Solder. 













Brass. 


Zinc. 


Tin. 




Parts. 


Very refractory 


85.42 


12.58 





Refractory 








7 
3 


1 

1 


— 


(< 










4 


1 


— 


Readily fusible 
it 










5 
5 


2 
4 


— 


Half wbite 

a 

White 










12 
44 

40 


5 

20 
2 


1 

2 

8 


cc 










22 


2 


4 


(< 










18 


12 


30 


Very ductile 










78.25 


17.25 


— 



c. Silver Solder. 



Brass silver solder 
Hard silver solder 
Very hard solder 
Middling hard solder 
Soft silver solder 
Silver solder for cast iron 
Silver solder for steel . 



1 
4 
40 
40 
32 
20 
30 



Silver. Copper. Brass. Tin. Zinc, 



Parts. 



1 

10 


1 


— 


__ 


___ 


10 


40 


10 


— 


32 


2 


30 


— 


— 


10 


— 


— 



— — 10 



378 



ELECTRO-DEPOSITION OF METALS. 

d. Gold Solder. 



Gold. 



Silver. Copper. 



Zinc. 



Parts. 



Hard solder for fineness 750 
Soft " " " 750 

Solder for fineness 583 

583 

less than 583 



Solder readily fusible 



for yellow gold 



9 
12 

3 

2 

1 

1 

1 
11.94 
10 



2 


1 


7 


3 


2 


1 


0.5 


0.5 


2 


1 


2 


— 


— 


2 


54.74 


28.17 


5 


— 



5.01 
1 



Table of the melting points of some metals. 



Metals. 


Degrees, 
Fahrenheit. 


Metals. 


Degrees, 
Fahrenheit. 


Tin . 

Lead 

Zinc .... 

Antimony . 

Brass 

Copper 


458.6 
599.4 
773.6 
809.6 

1859 

1994 


Gold 

Iron, crude 

Nickel 

Steel 

Iron, bar . 


2372 

2912 to 3092 

2912 

3092 to 3452 

3452 to 3812 



Table of high temperatures. 




Description. 


Degrees, 
Fahrenheit. 


Description. 


Degrees, 
Fahrenheit. 


Incipient red heat 

A red heat 

A dull red heat visible 

in daylight 
Heat of a common fire 
A full red heat . 
Dull red heat 


977 
980 

1000 
1140 
1200 
1310 


An orange red heat . 
A bright red heat 
A dull white heat 
A white heat 
Heat of a good blast 
furnace . 


1700 
1873 

1996 
3000 

3300 



Table of the specific gravity and content of solutions of potassium 
carbonate at 5T.2° Fahrenheit, according to Gerlach. 



Potassium 




Potassium 




Potassium 




carbonate, 


Specific gravity. 


carbonate, 


Specific gravity. 


carbonate, 


Specific gravity. 


per cent. 




per cent. 




per cent. 




2 


1.01829 


20 


1.19286 


38 


1.39476 


4 


1.03658 


22 


1.21402 


40 


1.41870 


6 


1.05513 


24 


1.23517 


42 


1.44338 


8 


1.07396 


26 


1.25681 


44 


1.46807 


10 


1.09278 


28 


1.27893 


46 


1.49314 


12 


1.11238 


30 


1.30105 


48 


1.51861 


14 


1.13199 


32 


1.32417 


50 


1.544^8 


16 


1.15200 


34 


1.34729 


52 


. 1.57048 


18 


1.17243 


36 


1.37082 


52.024 


1.57079 



USEFUL TABLES. 



379 



Table showing the specific gravity of sulphuric acid at 59° 
according to Kolb. 







100 parts by 


One liter 






100 parts by 


One liter 






weight 


contains in 






weight 


contains in 


» a 


Specific 


contain 


kilogrammes 




Specific 


contain 


kilogrammes 


(D 3 


gravity. 






gravity. 






bcpq 
P 




so 3 . 


H 2 S0 4 . 


so 3 . 


H 2 S0 4 . 


8* 
ft 




so 3 . 


HoS0 4 . 


S0 3 . 


H 2 S0 4 . 





1.000 


0.7 


0.9 


0.007 


0.009 


34 


1.308 


32.8. 


40.2 


0.429 


0.526 


1 


1.007 


1.5 


1.9 


0.015 


0.019 


35 


1.320 


33.8 


41.6 


0.447 


0.549 


2 


1.014 


2.3 


2.8 


0.023 


0.028 


36 


1.332 


35.1 


43.0 


0.468 


0.573 


3 


1.022 


3.1 


3.8 


0.032 


0.039 


37 


1.345 


36.2 


44.4 


0.487 


0.597 


4 


1.029 


3.9 


4.8 


0.040 


0.049 


38 


1.357 


37.2 


45.5 


0.505 


0.617 


5 


1.037 


4.7 


5.8 


0.049 


0.060 


39 


1.370 


38.3 


46 9 


0.525 


0.642 


6 


1.045 


5.6 


6.8 


0.059 


0.071 


40 


1.383 


39.5 


48.3 


0.546 


0.668 


7 


1.052 


6.4 


7.8 


0.067 


0.082 


41 


1.397 


40.7 


49.8 


0.569 


0.696 


8 


1.060 


7.2 


8.8 


0.076 


0.093 


42 


1.410 


41.8 


51.2 


0.589 


0.722 


9 


1.067 


8.0 


9.8 


0.085 


0.105 


43 


1-424 


42.9 


52.8 


0.611 


0.749 


10 


1.075 


8.8 


10.8 


0.095 


0.116 


44 


1.438 


44.1 


54.0 


0.634 


0.777 


11 


1.083 


9.7 


11.9 


0.105 


0.129 


45 


1.453 


45.2 


55.4 


0.657 


0.805 


12 


1.091 


10.6 


13.0 


0.116 


0.142 


46 


1.468 


46.4 


56.9 


0.681 


0.835 


13 


1.100 


11.5 


14.1 


0.126 


0.155 


47 


1.483 


47.6 


58.3 


0.706 


0.864 


14 


1.108 


12.4 


15.2 


0.137 


0.168 


48 


1.498 


48.7 


59.6 


0.730 


0.893 


15 


1.116 13.2 


16.2 


0.147 


0.181 


49 


1.514 


49.8 


61.0 


0.754 


0.923 


16 


1.125 


14.1 


17.3 


0.159 


0.195 


50 


1.530 


51.0 


62.5 


0.780 


0.956 


17 


1.134 


15.1 


18.5 


0.172 


0.210 


51 


1.540 


52.2 


64.0 


0.807 


0.990 


18 


1.142 


16.0 


19.6 


0.183 


0.224 


52 


1.563 


53.5 


65.5 


0.836 


1.024 


19 


1.152 


17.0 


20.8 


0.196 


0.233 


53 


1.580 


54.9 


67.0 


0.867 


1.059 


20 


1.162 


18.0 


22.2 


0.209 


0.258 


54 


1.597 


56.0 


68.6 


0.894 


1.095 


21 


1.171 


19.0 


23.3 


0.222 


0.273 


55 


1.615 


57.1 


70.0 


0.922 


1.131 


22 


1.180 


20.0 


24.5 


0.236 


0.289 


56 


1.634 


58.4 


71.6 


0.954 


1.170 


23 


1.190 21.1 


25.8 


0.251 


0.307 


57 


1.652 


59.7 


73.2 


0.986 


1.210 


24 


1.200 


22.1 


27.1 


0.265 


0.325 


58 


1.672 


61.0 


74.7 


1.019 


1.248 


25 


1.210 


23.2 


28.4 


0.281 


0.344 


59 


1.691 


62.4 


76.4 


1.055 


1.292 


26 


1.220 


24.2 


29.6 


0.295 


0.361 


60 


1.711 


63.8 


78.1 


1.092 


1.336 


27 


1.231 


25 3 


31.0 


0.311 


0.382 


61 


1.732 


65.2 


79.0 


1.129 


1.384 


28 


1.241 


26.3 


32.2 


0.326 


0.400 


62 


1.753 


66.7 


81.7 


1.169 


1,432 


29 


1.252 


27.3 


33.4 


0.342 


0.418 


63 


1.774 


68.7 


84.1 


1.219 


1.492 


30 


1.263 


28.3 


34.7 


0.357 


0.438 


64 


1.796 


70.6 


86.5 


1.268 


1.554 


31 


1.274 


29.4 


36.0 


0.374 


0.459 


65 


1.819 


73.2 


89.7 


1.332 


1.632 


32 


1.285 


30.5 


37.4 


0.392 


0.481 


66 


1.842 


81.6 


100.0 


1.503 


1.842 


33 


1.297 


31.7 


38.8 


0.411 


0.503 















380 



ELECTEO-DEPOSITION OF METALS. 



Table of the specific gravity and content of nitric acid, 
according to KoTb. 







100 parts 


100 parts 






100 parts 


100 parts 


^a5 




contain at 


contain at 


\<o 




contain at 


contain at 


gg 


Specific 


32° F. 


59° F. 


»S 


Specific 


32° F. 


59° F. 


O 03 


gravity. 








V 2 

&3 


gravity. 






&« 


















5 




HN0 3 . 


N 2 5 . 


HN0 3 . 


N 2 5 . 


ft 




HNO3. 


N 2 5 . 


HNO3. 


N 2 5 . 





1.000 


0.0 


0.0 


0.2 


0.1 


28 


1.242 


36.2 


31.0 


38.6 


33.1 


i 


1.007 


1.1 


0.9 


1.5 


1.3 


29 


1.252 


37.7 


32.3 


40.2 


34.5 


2 


1.014 


2.2 


1.9 


2.6 


2.2 


30 


1.261 


39.1 


33.5 


41.5 


35.6 


3 


1.022 


3.4 


2.9 


4.0 


3.4 


31 


1.275 


41.1 


35.2 


43.5 


37.3 


4 


1.029 


4.5 


3.9 


5.1 


4.4 


32 


1.286 


42.6 


36.5 


45.0 


38.6 


5 


1.036 


5.5 


4.7 


6.3 


5.4 


33 


1.298 


44.4 


38.0 


47.1 


40.4 


6 


1.044 


6.7 


5.7 


7.6 


6.5 


34 


1.309 


46.1 


39.5 


48.6 


41.7 


7 


1.052 


8.0 


6.9 


9.0 


7.7 


35 


1.321 


48.0 


41.1 


50.7 


43.5 


8 


1.060 


9.2 


7.9 


10.2 


8.7 


36 


1.334 


50.0 


42.9 


52.9 


45.3 


9 


1.067 


10.2 


8.7 


11.4 


9.8 


37 


1.346 


51.9 


44.5 


55.0 


47.1 


10 


1.075 


11.4 


9.8 


12.7 


10.9 


38 


1.359 


54.0 


46.3 


57.3 


49.1 


11 


1.083 


12.6 


10.8 


14.0 


12.0 


39 


1.372 


56.2 


48.2 


59.6 


51.1 


12 


1.091 


13.8 


11.8 


15.3 


13.1 


40 


1.384 


58.4 


50.0 


61.7 


52.9 


13 


1.100 


15.2 


13.0 


16.8 


14.4 


41 


1.398 


60.8 


52.1 


64.5 


55.3 


14 


1.108 


16.4 


14.0 


18.0 


15.4 


42 


1.412 


63.2 


54.2 


67.5 


57.9 


15 


1.116 


17.6 


15.1 


19.4 


16.6 


43 


1.426 


66.2 


56.7 


70.6 


60.5 


16 


1.125 


18.9 


16.2 


20.8 


17.8 


44 


1.440 


69.0 


59.1 


74.4 


63.8 


17 


1.134 


20.2 


17.3 


22.2 


19.0 


45 


1.454 


72.2 


61.9 


78.4 


67.2 


18 


1.143 


21.6 


18.5 


23.6 


20.2 


46 


1.470 


76.1 


65.2 


83.0 


71.1 


19 


1.152 


22.9 


19.6 


24.9 


21.3 


47 


1.485 


80.2 


68.7 


87.1 


74.7 


20 


1.161 


24.2 


20.7 


26.3 


22.5 


48 


1.501 


84.5 


72.4 


92.6 


79.4 


21 


1.171 


25.7 


22.0 


27.8 


23.8 


49 


1.516 


88.4 


75.8 


96.0 


82.3 


22 


1.180 


27.0 


23.1 


29.2 


25.0 


49.5 


1.524 


90.5 


77.6 


98.0 


84.6 


23 


1.190 


28.5 


24.4 


30.7 


26.3 


49.9 


1.530 


92.2 


79.0 


100.0 


85.71 


24 


1.199 


29.8 


25.5 


32.1 


27.5 


50.0 


1.532 


92.7 


79.5 


— 


— 


25 


1.210 


31.4 


26.9 


33.8 


28.9 


50.5 


1.541 


95.0 


81.4 


— 


— 


26 


1.221 


33.1 


28.4 


35.5 


30.4 


51.0 


1.549 


97.3 


83.4 


— 


— 


27 


1.231 


34.6 


29.7 


37.0 


31.7 


51.5 


1.559 


100.0 


85.71 


— 


— 



USEFUL TABLES. 



381 



Table showing the specific gravity of sal ammoniac solution at 
66.2° F., according to Schiff. 



Content of 

the solution, 

per cent. 


Specific 
gravity. 


Content of 

the solution, 

per cent. 


Specific 
gravity. 


Content of 

the solution, 

per cent. 


Specific 
gravity. 


1 
2 
3 
4 
5 
6 
7 
8 
9 
10 


1.0029 
1.0058 
1.0087 
1.0116 
1.0145 
1.0174 
1.0203 
1.0233 
1.0263 
1.0293 


11 

12 
13 
14 
15 
16 
17 
18 
19 
20 


1.0322 
1.0351 
1.0380 
1.0409 
1.0438 
1.0467 
1.0495 
1.0523 
1.0551 
1.0579 


21 

22 
23 
24 
25 
26 
27 
28 
29 
30 


1.0606 
1.0633 
1.0660 
1.0687 
1.0714 
1.0741 
1.0768 
1.0794 
1.0820 
1.0846 



Table showing the electrical resistance of pure copper, wire 
■ of various diameters. 







Number of 






Number of 


No. of wire, 
Birmingham 


Resistance of 


feet required 
to give 


No. of wire, 
Birmingham 


Resistance of 


feet required 
to give 


wire gauge. 




resistance 
of 1 ohm. 


wire gauze. 




resistance 
of 1 ohm. 


0000 


0.0000516 


19358 


17 


0.00316 


316.1 


000 


0.0000589 


16964 


18 


0.00443 


225.5 


00 


0.0000737 


13562 


19 


0.00603 


165.7 





0.0000922 


10857 


20 


0.00869 


115.1 


1 


0.000118 


8452.6 


21 


0.01040 


96.2 


2 


0.000132 


7575.L 


22 


0.01358 


73.6 


3 


0.000159 


6300.1 


23 


0.01703 


58.7 


4 


0.000188 


5319.9 


24 


0.02200 


45.5 


5 


0.000220 


4545,9 


25 


0.02661 


37.6 


6 


0.00C258 


3870.3 


26 


0.03286 


30.4 


7 


0.000329 


3043.4 


27 


0.04159 


24.0 


8 


0.000391 


2557.1 


28 


0.05432 


18.4 


9 


0.000486 


2057.7 


29 


0.06300 


15.9 


10 


0.000593 


1686.5 


30 


0.07393 


13.5 


11 


0.000739 


1352.5 


31 


0.10646 


9.4 


12 


0.000896 


1116.0 


32 


0.13144 


7.6 


13 


0.001180 


847.7 


33 


0.16634 


6.0 


14 


0.001546 


647.0 


34 


0.21727 


4.6 


15 


0.002053 


487.0 


35 


0.42583 


2.4 


16 


0.002520 


396.8 


36 


0.66537 


1.5 



382 



ELECTRO-DEPOSITION OF METALS. 



Table showing actual diameters in decimal parts of an inch 
corresponding to the numbers of various wire gauges. 



No. of wire 
gauge. 


Roebling. 


Brown & 
Sharpe. 


Birmingham 
or Stubs. 


English legal 
standard. 


Old English 
or London. 


000000 


.46 




_ 


.464 




00000 


.43 


— 


— 


.432 


— 


0000 


.393 


.46 


.454 


.4 


.454 


000 


.362 


.40964 


.425 


.372 


.425 


00 


.331 


.3648 


.380 


.348 


.38 





.307 


.32495 


.340 


.324 


.34 


1 


.283 


.2893 


.3 


.3 


.3 


2 


.263 


.25763 


.284 


.276 


.284 


3 


.244 


.22942 


.259 


.252 


.259 


4 


.225 


.20431 


.238 


.232 


.238 


5 


.207 


.18194 


.22 


.212 


.22 


6 


.192 


.16202 


.203 


.192 


.203 


7 


.177 


.14428 


.18 


.176 


.18 


8 ' 


.162 


.12849 


.165 


.16 


.165 


9 


.148 


.11443 


.148 


.144 


.148 


10 


.135 


.10189 


.134 


.128 


.134 


11 


.120 


.09074 


.12 


.116 


.12 


12 


.105 


.08081 


.109 


.104 


.109 


13 


.092 


.07196 


.095 


.092 


.095 


14 


.08 


.06408 


.083 


.08 


.083 


15 


.072 


.05706 


.072 


.072 


.072 


16 


.063 


.05082 


.065 


.064 


.065 


17 


.054 


.04525 


.058 


.056 


.058 


18 


.047 


.0403 


.049 


.048 


.049 


19 


.041 


.03589 


.042 


.04 


.04 


20 


.035 


.03196 


.035 


.036 


.035 


21 


.032 


.02846 


.032 


.032 


.0315 


22 


.028 


.02534 


• .028 


.028 


.0295 


23 


.025 


.02257 


.025 


.024 


.027 


24 


.023 


.0201 


.022 


.022 


.025 


25 


.02 


.0179 


.02 


.02 


.023 


26 


.018 


.01594 


.018 


.018 


.0205 


27 


.017 


.01419 


.016 


.0164 


.01875 


28 


.016 


.0]264 


.014 


.0148 


.0165 


29 


.015 


.01125 


.013 


.0136 


.0155 


30 


.014 


.01002 


.012 


.0124 


.01375 


31 


.0135 


.00893 


.010 


.0116 


.01225 


32 


.013 


.00795 


.009 


.0108 


.01125 


33 


.011 


.00708 


.008 


.01 


.01025 


34 


.01 


.0063 


.007 


.0092 


.0095 


35 


.0095 


.00561 


.005 


.0084 


.009 


36 


.009 


.005 


.004 


.0076 


.0075 



INDEX. 



ACETIC acid as an addition to 
nickel baths, 137 
Acid, acetic, as an addition to nickel 
baths, 137 
and metal, regaining of the, from 

exhausted dipping baths, 124 
arsenious, 350, 351 
benzoic, as an addition to nickel 

baths, 137, 138 
boracic, 350 
boric, 350 

as an addition to nickel 
baths, 137, 138. 
chromic, 351 
citric, 350 

as an addition to nickel 
baths, 137 
free, determination of, in gal- 

vanoplastic baths, 284 
hydrochloric, 349 
hydrocyanic, 349, 350 
hydrosulphuric, 352, 353 
mixtures, recovery of gold from, 

251 
muriatic, 349 
nitric, 349 

potassium carbonate, 361 
prussic, 349, 350 
sulphuric, 348, 349 
sulphurous, poisoning by, 347, 

348 
sulphydric, 352, 353 
Acidity and alkalinity, testing the, of 

nickel baths, 138 
Acids, 348-351 

neutralizing the action of, upon 
the enamel of the teeth, etc., 
345 
organic, salts of the, 368, 369 
Accumulators and their use, 295, 296 
Aerometer, the, not reliable for esti- 
mating the density of the baths, 
128, 129 



Alkalies and alkaline earths, 351, 352 

poisoning by, 347 
Alkaline earths and alkalies, 351, 352 
Alkalinity and acidity, testing the, of 

nickel baths, 138 
Alloy containing nickel, deposition of 

an, 177 
Alloying of the deposit with the basis- 
metal, 133 
Alloys and solders, table showing the 
composition of the most usual, 
375-378 
metallic, first deposition of, 22 
for the production of moulds, 
304 
of nickel, deposits of, 177-179 
table of, 376 
Alternate current machine, 62 

currents, 37 
Aluminium baths, 272, 273 
deposition of, 272, 273 
potassium sulphate, 363 
properties of, 272 
Amalgamation of the zinc of elements, 

45, 46 
American double polishing lathes, 
112, 113 
" Giant" dynamo-machine, 332, 

333 
types, recent, of batteries and 
dynamo-machines, 329-333 
Ammetre or ampfere-metre, 93 
Ammonia, 352 

sulphydrate or hvdrosulphate of, 
353 
Ammonium-alum, 363 
chloride, 354 
hydrate, 352 
phosphate, 368 
sulphate, 362, 363 
sulphide, 353 
Ampere, the, 42 

theory of magnetism of, 25 



384 



INDEX. 



Ampere-metre or ammetre, 93 
Amperes, table showing the value of 
equal current- volumes as expressed 
in, per square decimetre, per square 
foot, and per square inch, 372, 373 
Anions, 38 
Anode, 38 

and object- wires, coupling of the, 
with the resistance boards, 
voltmeter, shunt, and baths, 
95-97 
or positive wire, 87 
rods, connection of the, 89 
solution for transferring any cop- 
per-zinc alloy serving as, 197 
Anodes, arrangement of the, 88, 89 
choice of, 132, 133 
hooks for suspending the, 89, 90 
insoluble, for nickel baths, im- 
practicability of, 145, 146 
nickel, 144-147 

reddish tinge of, 147 
silver, 202-209 
surface of, 80 
used in brassing, 195 
in bronzing, 199 
in nickeling sheet-zinc, 166 
Antidotes for poisoning by chemicals, 

346-348 
Antimony and arsenic deposits of, by 
contact and immersion, 271, 
272 
baths, formulae for, preparation 

and properties of, 270 
butter of, 355 
deposit, explosive property of 

the, 270 
deposition of, 269, 270 
potassium tartrate, 369 
properties of, 269 
sulphide, 353, 354 
trichloride, 355 
Antique silvering, 228 
Apparatus and instruments, 329-344 

auxiliary, 81 
Apparatuses, cleansing and rinsing, 

90, 91 
Aqua fortis, 349 
Argentiferous pastes, composition of, 

223 
Armature and dynamo, Brush's, 66, 67 

Gramme, 62-64 
Arrangement of electro-plating estab- 
lishments in general, 75-101 
Arrangements with dynamo-electric 
machines, 91-101 



Arsenic, 350, 351 

and antimony deposits of, by con- 
tact and immersion, 271, 272 
baths, formulas for, preparation 

and properties of, 271 
deposition of, 270-272 
poisoning by, 347 
properties of, 270, 271 
trisulphide, 354 
white, 350, 351 
Arsenious acid, 350, 351 

effect of, on brassing, 193 
chloride, 355 
sulphide, 354 
Art-castings, coppered, inlaying with 

black, of depressions of, 191 
Articles, metallic, chemical treatment 
of the, 119-126 
mechanical treatment of the, 

102-119 
treatment of the, 102-126 
Asphalt, pavement of, 77 
Astatic galvanometer, 34 
Atoms, 38 
Auric chloride, 357 
Auxiliary apparatus, 81 



BACCO'S copper bath for copper- 
ing zinc by immersion, 190 
Backing, metal-, composition of, 297 

the deposit or shell, 296, 297 
Baking powder, 361 
Balloons and flasks, glass, 340 
Bath, agitation of the, 129-131 
bright dipping, 120, 121 
copper, for the cell apparatus, 277 
electrolytic, conditions for the 
good performance of a, 133 
requirements for a, 129 
for galvanoplastic operations with 
gold, 316 
with silver, 316 
Baths, aluminium, 272, 273 

antimony, formulae for, prepara- 
tion and properties of, 270 
arsenic, formulas for, preparation 

and properties of, 271 
boiling of, 131 

brass, formulas for, preparation, 
properties, and treatment of, 
192-197 
cobalt, 179 

concentration of the, 128, 129 
containing potassium cyanide, 
holders for, 88 



INDEX. 



385 



Baths- 
copper, for galvanoplastic depo- 
sitions with a separate 
source of current, 280, 
281 
formulae for, preparation 
and properties of, 182- 
187 
without potassium cyanide, 
185, 186 
feeding of the, with the current, 

97. 
for gilding by dipping, 247, 248 
for hard nickeling, 172, 173 
for silvering by immersion, 219, 

220. 
galvanoplastic, current densities 
for, 281 
determination of free acid 
in, 284 
of the content of copper 
in, 284, 285 
gold, formulas for, preparation 

and properties of, 232-236 
importance of the purity of the 

chemicals for the, 127, 128 
iron, management of, 268 
lead, formulas for, preparation 

and properties of, 265, 266 
nickel, formulae for and prepara- 
tion of, 138-144 
palladium, 257 

platinum, formulae for, prepara- 
tion and properties of, 251-255 
recovery of nickel from old, 174, 

175 
resistance boards, voltmeter, and 
shunt, coupling of the, with 
the object and anode wires, 
95-9 7 
securing lasting qualities to the, 

132 
silver, formulae for, preparation 
and properties of, 200-202 
treatment of, 202-209 
steel, formulae for, prepaiation 

and properties of, 267 
substitute lor boiling, 131' 
temperature of the, 76, 131 
tin, formulae for, preparation and 

properties of, 258, 259 
vats for, 87, 88 

for heating, 88 
Batteries and dynamo machines, re- 
cent American types of, 329- 
333 
25 



Batteries — 

dipping or bichromate, 55-57 
Battery, copper bath for galvanoplas- 
tic depositions with the, 280 
Fein's bichromate, 55 
galvanoplastic depositions with 

the, 279 
Keiser & Schmidt's bichromate, 

55 
Stoehrer's, 57 
Baume's hydrometer, 342 
Beardslee, G. W., cobalt solution re- 
commended by, 180, 181 
Becquerel's element, 47 
Benzine, use of, for the removal of 

grease, 125, 126 
Benzoic acid as an addition to nickel 

baths, 137, 138 
Bertrand's palladium bath, 257 

process for depositing aluminium, 
272 
Bicarbonate of potash, 361 

of soda, 361 
Bichromate element, bottle form of, 
56, 57 
or dipping batteries, 55-57 
Binding posts and rod connections, 
336 
screws, forms of, 89 
Bird, production of the amalgams of 

potassium and sodium by, 20 
Bisulphide of carbon as an addition to 

nickel baths, 143, 144 
Black-lead, gilt and silvered, 291, 292 
Black-leaded surface, coppering the, 

291 
Black- leading, discovery of, 21 
machines, 289, 290 
the moulds, 289-292 
Black nickeling, 268 

sulphide of antimony, 353 
Blue vitriol, 364 

pure crystallized, table of 
the content of, 277 
Bobs for polishing sheet zinc, con- 
struction of, 159, 160 
polishing, 112 
Boettger's, Prof., observations on the 
deposition of nickel, 21, 22 
platinum bath, 252 
process of coloring iron blue, 325 
tinning solution, 261 
Boiling and contact, nickeling by, 
175-177 
tinning by, 260-262 
Book-plates, finishing of, 298, 299 



386 



INDEX. 



Boracic acid, 350 
Boric acid, 350 

as an addition to nickel 

baths, 137, 138 
nickel baths containing, 141, 
142 
Bouant's process of amalgamating the 

zinc of elements, 45, 46 
Box, tumbling, 106, 107 
Brandley's directions for gelatine 

moulds, 310, 311 
Brass and bronzes, coloring of, 320- 
324 
and copper articles, small, tin- 
ning solution for, 261 
castings, grinding of, 

111 
deposits, polishing of, 

117 
sheets, nickeling of, 167, 

168 
to coat with zinc, 264 
articles, cheap, nickel bath for, 

140 
baths, formulae for, preparation, 
properties, and treatment 
of, 192-197 
management of, 195, 196 
bronze, and copper, deposition 

of, 181-200 
dark nickeling upon, 143 
Ebermayer's experiments in col- 
oring," 323, 324 
pickling of, 120 
potassium cyanide as a pickle for, 

121 
properties of, 191, 192 
red, 191, 192 

removal of oxide from, 126 
sheets, grinding of, 111 
treatment of, for silvering by 

weight, 209, 210 
various colors upon, 319, 320 
yellow, 191, 192 
Brassed articles, inlaying with black, 

of, 198 
Brassing, anodes used in, 195 
by contact and dipping, 198 
color of, 194, 195 
(cuivre-poli deposit), 191-198 
effect of arsenious acid on, 193 
execution of, 197, 198 
sheet zinc, 164, 165 
Bright Platinum Plating Co., of Lon- 
don, platinum bath, patented by 
the, 252 



Britannia metal, cleansing and silver- 
ing of, 217 
or white me.tal, silvering of, 216, 

217 
quicking solution for, 217 
removal of oxide from, 126 
Bronze Barbedienne on brass, 321, 
322 
brass, and copper, deposition of, 

181-200 
-like patina on tin, 326 
nickel, 177 
pickling of, 120 
Bronzes and brass, coloring of, 320- 

324 
Bronzing, 198-200 

anodes used in, 199 
on zinc, 324, 325 
Bruce, the addition of bisulphide of 
carbon to nickel baths, recom- 
mended by, 143, 144 
Brugnatelli, discovery of electro-gild- 
ing by, 1 9 
Brush armature and dynamo, 66, 67 

-coppering, 190 
Brushes, 337-339 

fibre, 110 
Bunsen cell, improved, 330, 331 
elements, 49-52 
closet for, 76 
manipulation of, 51, 52 
Burning or over-nickeling, 149 
Burnishing, 114 

deposits of gold, silver, and plati- 
num, 118 
of silvered articles, 215, 216 
operation of, 118 
tools, 118, 119 
Busts, vases, etc., galvano-plastic re- 
production of, 302-307 
Butter of antimony, 355 
of zinc, 355, 356 



CALCIUM carbonate, 361 
hydrate, 352 
Capsules or dishes, evaporating, 340 
Carbon disulphide or bisulphide, 353 
Carbonates, 360-362 
Carlisle and Nicholson, decomposi- 
tion of water by, 18 
Cast and wrought iron articles, solution 
for coating with bronze, 
198, 199 
pickling of, 119, 120 
brass bath for, 197 



INDEX. 



387 



Castings, copper and brass, grinding 
of, 111 
zinc, grinding of, 111, 112 
Casts from metallic coins and medals, 

305 
Cathode, 38 
Cations, 38 

Cell apparatus, construction of, 274, 
275 
copper bath for the, 277 
French form of, 276 
galvano- plastic deposition in 

the, 274, 278 
German form of, 276 
Cement, pavement of, 77 
Centimetre — gramme — second sys- 
tem, 42 
Chain, galvanic, 28 
Chalk, 361 

Chemical actions of the electrical cur- 
rent, 37-40 
and electro-chemical equivalents, 

table of, 371, 372 
products used in the electro- 
plating art, 348-369 
treatment of the metallic articles, 
119-126 
Chemicals, importance of the purity 
of, 127, 128 
poisoning by, and the antidotes, 
346-348 
Chile saltpetre, 366 
Chlorine combinations, 354-357 

poisoning by, 347, 348 
Christofle & Co., replacement of bat- 
teries by magneto- electrical ma- 
chines, by, 22 
Chromic acid, 351 
Citric acid, 350 

as an addition to nickel baths, 
137 
Clamond's thermo-pile, 58, 59 
Clarke and Saxton, improvements in 

the electrical machine by, 60, 61 

Clausius's theory of molecules, 38, 39 

Cleansing and rinsing apparatuses, 90, 

91 

of the objects, 99, 100 

Cliches, electrotypes, etc., nickeling 

of, 172, 174 
Cobalt-ammonium sulphate, 365 

and nickel, deposition of, 135- 

181 
and nickel solutions, Warren's, 

154, 155 
carbonate, 362 



Cobalt- 
chloride, 356 

experiments in stripping the, 
from cobalted copper plates, 
180 
properties of, 1 79 
solution, recommended by G. W. 
Beardslee, 180, 181 
Warren's, 180 
sulphate, 365 
Cobalting, 179-181 
by contact, 181 
Coins and medals, metallic, taking 

casts from, 305 
Cold silvering with paste, 223 
Coloring of brass and bronzes, 320- 
324 
of copper, 317-320 
of gilding, 243-245 
of iron, 325, 326 
of silver, 326 
of tin, 326 
patinizing, oxidizing, etc., of 

metals, 316-326 
zinc, 324, 325 
Colors, iridescent, production of, 20, 

266 
Conducting rods, 88 

salt, best basis for the, 137 
salts, choice of, 136, 13 7 
wire, rule for determining the 
direction of the magnetic needle 
to the, 33 
wires, 334-336 

for dynamos, calculating the 
thickness of the, 101 
Conductor, resistance of a, 29 
Conductors, good and bad, 26 
Contact and boiling, nickeling by, 
175-177 
and dipping, brassing by, 198 

coppering by, 189, 190 
and immersion, antimony and 

arsenic deposits by, 271, 272 
cobalting by, 181 
current, electric, discovery of the, 

17, 18 
electro-deposition by, 133, 134 
gilding by, 247 
leading by, 266 
platinizing by, 256 
silvering by, 2i 9 
steeling by, 269 
tinning by, 260-262 
zincking iron by, 264 
Continuous current machine, 62 



388 



INDEX. 



Copper acetate, 369 

and brass articles, small, tinning 
solution for, 261 
castings, grinding of, 1 1 1 
deposits, polishing of, 

117 
sheets, nickeling of, 167, 

168 
to coat with zinc, 264 
copper-alloys, most suitable 
current density for nickel 
ing, 150 
articles, stripping the gold from, 

249, 250 
bath for the cell apparatus, 277 
galvanoplastic, contrivances 
for the motion of, 282, 283 
baths for galvanoplastic deposi- 
tions with a separate source 
of current, 280, 281 
formulae for, preparation and 

properties of, 182-187 
without potassium cyanide, 
185, 186 
brass and bronze, deposition of, 

181-200 
carbonate, 362 
chloride, 355 
coloring of, 317-320 
current- strength for the galvano- 
plastic deposition of, 294, 295 
cyanides, 359 
dark nickeling upon, 143 
deposit, thick, to surround the 
mercury vessels of thermome- 
ters with a, 313 
deposits, polishing of, 188 
determination of the content of, 
in galvanoplastic baths, 284, 
285 
massive, various colors upon, 319, 

320 
objects, bright-dipping bath for, 
120,121 
preliminary pickle for, 120 
pickling of, 120 

plates, cobalted, experiments in 
stripping the cobalt from, 
180 
cobalting of, 179 
precipitated by electrolysis, prop- 
erties of, 273, 274 
printing plates, galvanoplastic 

copper baths for, 281 
production of a thin film of, on 
iron and steel objects, 190, 191 



Copper — 

properties of, 181, 182 
removal of oxide from, 126 
salts, poisoning by, 34 7 
sheets, grinding of, 111 
sulphate, 364 

solutions, table showing the 
specific electrical resist- 
ances of different, 373 
the most suitable dynamo for the 
galvanoplastic deposition of, 
294 
to coat wood with a galvanoplastic 

deposit of, 313 
treatment of, for silvering by 

weight, 209, 210 
wire, pure, of various diameters, 
table showing the electrical 
resistance of, 381 
silvering of, 226 
zinc alloys, solution for transfer- 
ring any, serving as anode, 
197 
Coppered art-castings, inlaying of de- 
pressions of, with black, 191 
articles, removal of hydrochloric 
acid from the pores of, 
188 
to be coated with another 
metal, treatment of, 189 
Coppering, 181-191 

by contact and dipping, 189, 190 

execution of, 187-189 

laces and tissues, 311, 312 

of eyes, 191 

of grasses, leaves, and flowers, 

312 
of needles, 191 
of steel pens, 191 
of zinc sheets, 165 
prevention of the appearance of 
small, dark, round stains in, 
188 
small articles en masse, 189 
solid and heavy, 187, 188 
the black-leaded surface, 291 
Cork, gilding with the, 248, 249 
Corvin's niello, 312 
Coulomb, law of, 27 

the, 42 
Counter- or polarizing-current, 152, 

153 
Coupling, mixed, 33 
of elements, 31-33 
for quantity, 32 
for tension, 32 



INDEX. 



389 



Coupling of elements — 

choice of the, 79, 80 
of the object and anode wires 
with the resistance boards, 
voltmeter, shunt, and baths, 
95-97 
Crane, Frederick, Chemical Co., 
zapon manufactured by the, 327, 
328 
Cream of tartar, 368 
Crucibles, 340, 341 

Cruikshank, electro-deposition of 
metals, noticed by, 19 
the trough battery devised by, 18 
Cubic nitre, 366 
Cuivre fume, 318 

poli deposit, 191-198 
Cupric sulphate, 364 
Cups, gilding of, 239, 240 
Current, best wire for conducting the, 
87 
counter- or polarizing, 152, 153 
densities for galvanoplastic baths, 

281 
density, calculating the weight of 
the deposit of silver from the, 
215 
electric, chemical actions of the, 
37-40 
discovery of the chemical 

actions of the, 37, 38 
effects of the 33, 
preparation of gold baths 
with the assistance of the, 
235 
reduction of a fluid by the, 
37 
feeding of the bath with the, 97 
galvanic or hydroelectric, 28 
primary, or inductive, 36 
quantity of, 30-33 
regulation of the, 92, 93 
regulator, 82 

rules for conducting the, 87 
secondary or induced, 36 
sources of, 44-74 
strength for brass baths, 192 
for gilding, 239 
for nickeling zinc sheets, 1 65, 

166 
for silver baths, 203 
for the galvanoplastic de- 
position of copper, 294, 
295 
suitable for nickeling, 148, 
149 



Current — 

volumes, table showing the value 
of equal, as expressed in 
amperes per square decimetre, 
per square foot, and per square 
inch, 372, 373 
Currents, alternate, 37 

extra, 37 
Cyanide, poisoning by, 346, 347 
Cyanides, 358-360 

alkaline, first employment of, 21 



DANIELL'S element, 47 
Davy, Sir Humphry, discovery 
of potassium and sodium by, 19 
Dead dip, 121, 122 

gilding, 242, 243 
Defective nickeling, to improve, 175 
Deposit, detaching the, from the 
mould, 296 
of German silver, French process 

for obtaining a, 178 
or shell, backing the, 296, 297 
penetration of the, into the basis- 
metal, 133 
Deposition, galvanoplastic, by the 
battery and dynamo, 
278-284 
in the cell-apparatus, 
274-278 
of aluminium, 272, 273 
of antimony, 269, 270 

arsenic, aluminium, 269-273 
of arsenic, 270-272 
of copper, brass, and bronze, 

181-200 
of gold, 232-251 
of iron, 266-269 
of lead, 265, 266 
of nickel and cobalt, 135-181 
of palladium, 257 
of platinum, 251-257 

and palladium, 251-257 
of silver, 200-231 
of" tin, 257-262 

zinc, lead, and iron, 257-269 
of zinc, 262-265 
Deposits, nickel, polishing of, 158 
of nickel alloys, 177-179 
polishing of the, 117-119 
scratch-brushing the, 114-117 
Dip, dead, 121, 122 
Dipping and contact, brassing by, 198 
coppering by, 189, 190 
baskets, 337 



390 



INDEX. 



Dipping — 

bath, bright, 120, 121 

baths, regaining the acid and 

metal from exhausted, 124 
or bichromate batteries, 55-57 
or immersion, gilding by, 247, 

248 
or pickling, 90 
Dishes or capsules, evaporating, 340 
Disks, grinding, 107-109 

treatment of, 108, 109 
polishing, 112 
Doctoring and the "doctor," 175 
Drum, tumbling, 106, 107 
Drying chamber, 101 
Du Fresne's method of gilding, 242 
Dun's potash element, 54, 55 
Dupr6, A., solution for filling the 

Bunsen element proposed by, 51 
Dust, contrivance for retaining the, 78 
Dynamo and armature, Brush's. 66, 
67 
Gramme, 62-65 
and magneto-electric machines, 

59-74 
copper bath for galvanoplastic 

depositions with the, 280 
electric machine, new, manufac- 
tured by the Hanson 
and Van Winkle Co., 
of Newark, N. J., 
331, 332 
what it is, 60 
machines, arrangements 
with, 91-101 
Fein's, 66 
galvanoplastic depositions with 

the, 280-284 
Krottlinger's, 70, 71 
Lahmeyer's, 71-73 
machine, American "Giant," 
332, 333 
transition of the magneto- 
electric machine to the, 
61 
machines and batteries, recent 

American types of, 329-333 
Schuckert's, 65, 66 
Siemens & Halske's, 69 
the most suitable for the galvano- 
plastic deposition of copper, 
294 
value of the, and its effect upon 
the electroplating industry, 73, 
74 
Weston's, 69, 70 



Dynamos, calculating the thickness of 
the conducting wires for, 101 

rules for setting up and running, 
91, 92 

various, 73 



EARTHS, alkaline, and alkalies, 
351, 352 
Ebermayer's experiments in coloring 
brass, 323, 324 
silver bath for immersion, 222 
Electrical machine, Pixii's, 60 
potential, 28 

resistance, table showing the, of 
pure copper wire of various 
diameters, 381 
resistances, specific, table show- 
ing the, of dif- 
ferent copper sul- 
phate solutions, 
373 
of different sul- 
phuric acid solu- 
tions, 373 
Electric-connection gripper, 292 

contact-current, discovery of the, 

17, 18 
current, effects of the, 33 

erroneous idea of the, 18 
generators, classes of, 62 
induction, discovery of, 20 
units, 41-43 
Electricity, 26-43 

and magnetism, 24-43 
Franklin's theory of, 27 . 
good and bad conductors of, 26 
kinds of, 26, 27 

production of, by the contact of 
metals and fluids, 28 
of various metals, 27, 28 
resinous or negative, 27 
Symer's theory of, 27 
vitreous or positive, 27 
Electro-chemical and chemical equiva- 
lents, table of, 371, 372. 
equivalents, 40, 41 
deposit of silver, heavy, baths 

for, 200-202 
deposited silvering, determina- 
tion of, 230 
deposition and fire-gilding, com- 
bination of, 242 
by contact, 133, 134 
of iron, principal use of, 266 
processes of, 127-134 



INDEX. 



391 



Electro — 

etching, 300, 301 
gilding, discovery of, 19 
magnetic machine, first, 20 
magnetism, 33-35 
magnets, 35 

metallurgy, historical review of, 
17-23 
origination of the term, 21 
motive force, 29, 42 

table of the, of elements, 
374 
nickeling, the process of, 147- 

153 
plated objects, polishing of, 117- 

119 
plating establishments, arrange- 
ment of, in general, 75- 
101 
arrangements in particular, 

79-101 
art, chemical products used 

in the, 348-369 
establishment, ground-plan 

of a, 97-101 
industry, effect of the dy- 
namo upon the, 73, 74 
mechanical treatment of the 
metallic articles before, 
102-114 
plant, parts of the, 79 
process, mechanical treat- 
ment of the articles, dur- 
ing and after, 114-119 
silvering, ordinary, bath for, 202 
Electrochromy, 266 
Electrodes, 38 
Electrolysis, 37-40 

consumption of power in the, 41 
definition of, 17 
Electrolyte, 38 
Electrolytic law, Faraday's, proved, 

20, 39, 40 
Electroscope, the, and its use, 26 
Electrotypes, cliches, etc., nickeling 
of, 172-174 
in iron, baths for the production 
of, 267 
Element, Becquerel's, 47 

bichromate, bottle form of, 56, 

57 
Daniell's, 47 
Dun's potash, 54, 55 
galvanic, 28 
Grove's, 48, 49 
Lallande and Chaperon's, 53, 54 



Element — 

Leclanche's, 53 
Meidinger, 48 
Smee's, 46, 47 
Elements, amalgamation of the zinc 
of the, 45, 46 
application of Ohm's law to the 

coupling of, 30, 31 
arrangement with, 79-91 
Bunsen's, 49-52 
choice of the coupling of, 79, 80 
coupling of, 31-33 

for quantity, 32 
galvanic, 44-57 
mixed coupling of the, 33 
proportion of the active zinc sur- 
face of the, 80 
table of the electro- motive force 

of, 374 
union or coupling of the, for 

tension, 32 
various, 54 

with their symbols, atomic 
weights, and specific gravities, 
table of, 370 
Elkington establishment, Birming- 
ham, contrivance in the, for keep- 
ing the articles in the silver bath in 
gentle motion, 207 
Elkingtons, the, progress in the gal- 

vanoplastic art due to the, 21 
Eisner's bronze bath, 199 

tinning bath, 261 
Emery, for grinding disks, 108 
Equivalents, chemical and electro- 
chemical, table of, 3 71, 372 
electro-chemical, 40, 41 
Etching ground, 301 
Evaporating dishes or capsules, 340 
Eyes and hooks, silvering of, 222, 
223 
coppering of, 191 
Extra currents, 37 



FARAD, the, 42 
Faradav, discoveries by, 20, 37, 
38, 59 
electrolytic laws of, 20, 39, 
40 
Fein's bichromate battery, 55 

dynamo, 66 
Ferric sulphide, 354 
Ferrous sulphate, 363, 364 
Fibre brushes, 110 
Field, magnetic, 25 



392 



INDEX. 



Filters, 342-344 

Fine wheel, 108 

Fire-gilding, combination of with 
electro-deposition, 242 

Flasks and balloons, glass, 340 

Floors of working-rooms, best material 
for, 77 

Flowers, coppering of, 312 

Fluids and metals, production of elec- 
tricity by the contact of, 28 

Foot-lathe, 112 

Force, electro- motive, 29, 42 
or power, 42 
region of the lines of, 60 

Forks and spoons, heavy coating of 
silver on the convex surfaces of, 
218 

Franklin's theory of electricity, 27 

French form of cell apparatus, 276 

Friction, gilding by, 248, 249 

Fuming liquor of Libadius, 355 

Fundamental system, 42 



GALVANI, Luigi, discovery of the 
electric contact-current by, 17, 18 
Galvanic element or galvanic chain, 28 
elements, 44-57 

thermo-piles, magneto- and 
dynamo-electric machines, 
44-74 
or hydro-electric current, 28 
Galvanometer and resistance board, 
arrangement of the, 84 
astatic, 34 

indications of the, 84-87 
sine, 34 
tangent, 34 
Galvanometers, 83 

galvanoscopes, or multipliers, 34 
Galvanoplastic baths, current-densities 
for, 281 
determination of free acid in, 
284 
of the content of copper 
in, 284, 285 
copper baths, contrivances for 

the motion of, 282, 283 
copy, to make a, from a metallic 

surface, 229, 300 
deposit of copper, to coat wood 

with a, 313 
deposition by the battery and 
dynamo, 278-284 
in the cell apparatus, 274- 
278 



Galvanoplastic deposition — 

of copper, the most suitable 

dynamo for the, 294 

depositions with a separate source 

of current, copper baths for, 

280, 281 

method for originals in high relief 

— Lenoir's process, 309, 310 
operations in iron, 313, 314 
in nickel, 314, 315 
in silver and gold, 315, 316 
process, discovery of the, 20 
reproduction of busts, vases, etc., 
302-307 
Galvanoplasty, 273-316 

special uses of, 311-316 
Galvanoscopes, galvanometers, or mul- 
tipliers, 34 
Gases, nitrous and hyponitric, poison- 
ing by, 347, 348 
Gauduin's copper bath, 186 
Gauze and wire, metallic, gilding of, 

245-247 
Gelatine moulds, 310, 311 
German form of cell apparatus, 276 
silver, French process for ob- 
taining a deposit of, 178 
or nickel articles, silvering 
of, 217 
silver, cleansing and sil- 
vering of, 217 
pickling of, 1 20 
removal of oxide from, 126 
sheets, grinding of, 111 
stripping the gold from, 249, 

250 
treatment of, for silvering by 

weight, 209, 210 
Watt's method for obtaining 
a deposit of, 178, 179 
Gilded articles, removing gold from, 
249, 250 
to give a rich appear- 
ance to, 244, 245 
Gilder's wax, formulas for, 244 
Gilding by contact, by immersion, 
and by friction, 247-249 
by weight, 240 
cold, baths for, 233, 234 
coloring of the, 243-245 
current-strength for, 239 
dead, 242, 243 
execution of, 238-241 
genuine, determinaton of, 250 
green, 241, 242 
hot, baths for, 234, 235 



INDEX. 



393 



Gilding — 

improving bad tones of, 245 
in the cold bath, process of, 240 
in the hot bath, process of, 240 
of metallic wire and gauze, 245- 

24 7 
preparation of the articles for, 

238, 239 
red, 241 
rose-color, 242 
with the cork, 248, 249 
with the rag, 248, 249 
with the thumb, 248, 249 
without a battery, 238 
Gilt and silvered black-lead, 291, 292 
Glass balloons and flasks, 340 
jars, 340 

metallization of, 313 
Glauber's salt, 362 
Gold and silver deposits, burnishing 
of, 118 
galvanoplastic operations in, 
315, 316 
bath, management of the, 236- 

238 
baths, formulae for, preparation 
and properties of, 232-236 
heating of, 237, 238 
recovery of gold from, 250, 

251 
vats for, 237 
chloride, 357 

deposit, coloring of the, 236 
deposition of, 232-251 
deposits, polishing of, 241 
incrustations with, 245 
properties of, 232 
recovery of, from acid mixtures, 
251 
from gold baths, 250, 251 
removing the, from gilded arti- 
cles, 249, 250 
silver and other metals, incrusta- 
tions with, 226, 227 
solder, 378 

varnishers, mode of operation of, 
328, 329 
Gore's experiments, 133 
Goutier, solution for coating wrought- 
and cast-iron articles with bronze, 
198, 199 
Goze's process for depositing alumin- 
ium, 272, 273 
Grained surface, pickle for the pro- 
duction of a, 124, 125 
watch parts, gilding of, 226 



Graining, 223-226 

Gramme dynamo machines, 23, 62- 

65 
Grasses, coppering of, 312 
Grease, removal of, 125, 126 

table for freeing the articles 
from, 100, 101 
Green gilding, 241, 242 

vitriol, 363, 364 
Grinding, 107-112 

and polishing-rooms, arrangement 

of, 78 
disks, 107-109 

treatment of, 108, 109 
execution of, 110 
lathes, 109-111 

or polishing sheet zinc, 160, 161 
Grove element, 4*, 49 
Gun-barrels, browning of, 325 
Gutta-percha, introduction for moulds 
of, 21 
moulding in, 286 



HANSON & Van Winkle Co., of 
Newark, N. J., the new dynamo 
electric machine, manufactured 
by the, 331, 332 
Hard nickeling, baths for, 172, 173 

solder, 377 
Heating, arrangements for, 76 
Hefner- Alteneck, dynamo machine 

of, 23 
Heliography, 301, 302 
Hess's solution for transferring any 
copper- zinc allov serving as anode, 
197 
Historical review of electro- metal- 
lurgy, 17-23 
Hollow-ware, cleansing and silvering 
of, 217 
gilding of, 239, 240 
Hooks and eyes, silvering of, 222, 
223 
for suspending the anodes, 89, 90 
Horn silver, 356, 357 
Horse-power, English, 43 

French, 43 
Hlibl, von, current-densities for gal- 
vanoplastic baths, accord- 
ing to, 281 
experiments on copper by, 
274 
Hydraulic press, 287, 288 
Hydrochlorate or muriate of zinc, 
355, 356 



394 



INDEX. 



Hydrochloric acid, 349 

removal of, from the pores 
of coppered articles, 188 
Hydrocyanate of silver, 360 

of zinc, 359, 360 
Hydrocyanic acid, 349, 350 

poisoning by, 346, 34 7 
Hydroelectric or galvanic current, 

28 
Hydrogen, sulphuretted, 352, 353 

poisoning by, 347 
Hydrometers, 341, 342 

table showing readings of differ- 
ent, 342 
Hydroplatinic chloride, 357 
Hydrosulphuric acid, 352, 353 
Hygienic rules for the work-shop, 345- 

348 
Hyponitric and nitrous gases, poison- 
ing by, 347, 348 



IDIOELECTBJCS, definition of, 
26 
Immersion and contact, antimony and 
arsenic deposits by, 271, 
272 
baths for tinning by, 260, 

261 
or dipping, gilding by, 247, 

248 
silvering by, 219-223 
Incrustations with silver, gold and 

other metals, 226, 227 
Induced or secondary current, 36 
Induction, 35-37 

definition of, 35 
electric, discovery of, 20 
Inductive or primary current, 36 
Instruments and apparatus, 329-344 
Ions, 38 

Iridescent colors, production of, 266 
Iron-ammonium sulphate, 364 

and steel articles, copper baths 
for, 182-184 
grinding of, 111 
tinning solution for, 261 
most suitable current-density 

for nickeling, 150 
objects, production of a thin 
film of copper on, 190, 
191 
removal of oxide from, 
126 
sheet, nickeling of, 168, 169 
articles, pickling of, 119, 120 



Iron articles — 

wrought and cast, solution 
for coating with bronze, 
198, 199 
baths, management of, 268 
brass bath for, 194 
castings, unground, brassing of, 

198 
coloring of, 325, 326 
dark nickeling upon, 143 
deep black deposit of, 268 
deposition of, 266-269 
galvanoplastic operations in, 313, 

314 
objects, badly rusted, to cleanse, 
119, 120 
nickel salts not to be used 

for nickeling, 136, 137 
nickeled, immersion of, in 
boiling linseed oil, 117 
ore, magnetic, 24 
pickle for, 119 

production of electrotypes in, 267 
protosulphate, 363, 364 
sulphate, 363, 364 
wrought and cast, brass bath for, 

197 
zincking of, by contact, 264 



JACOB Y, Prof., discovery of the 
?J galvanoplastic process by, 20 
Johnson and N orris's brass bath, 197 
Jordan, C. J., claim by, 20 
Joule's law, 41 



KAISER'S process of depositing 
an alloy containing nickel, 177 

Keiser & Schmidt's bichromate bat- 
tery, 55 

Kettles and boiling pans, 339 

Klein's bath for the production of 
electrotypes in iron, 267 

Knife blades, sharp surgical instru- 
ments, etc., nickeling of, 171, 172 

Knight, Silas P., black-leading pro- 
cess invented by, 290 

Krottlinger's dynamo, 70, 71 



LACES and tissues, Philipp's pro- 
cess for coating with copper, 311 , 
312 
Lacquering, 326-329 
Lahmeyer dynamo, 71-73 



INDEX. 



395 



Lallande and Chaperon's element, 53, 

54 
Lamp feet of cast zinc, nickeling of, 

151 
Lathe-brush, 116, 117 
Lathe for polishing silver plate and 

silver, 337 
Lathes, grinding, 109-111 
Law, Coulomb's, 27 
Joule's, 41 
Ohm's, 19, 30 
Laws, Faradav's electrolytic, 20, 39, 

40 
Lead acetate, 369 

baths, formula? for, preparation 

and properties of, 265, 266 
deposition of, 265, 266 
properties of, 265 
removal of oxide from, 126 
salts, poisoning by, 347 
Leading by contact, 266 
Leather, plates for the production of 

imitations of, 312, 313 
Leaves, coppering of, 312 
Leclanehe element, 53 
Length, unit of, 41 
Lenoir's process — galvanoplastic 
method for originals in high re- 
lief, 309, 310 
Libadius, fuming liquor of, 355 
Light and ventilation of work-rooms, 

75, 76 
Lime, burnt or quick, 352 
mixture, 125 

Vienna, constitution of, 109 
Line, neutral, 24 
Linseed oil, boiling, immersion of 

nickeled iron objects in, 117 
Liver of sulphur, 353 
Loadstone, 24 
Llidersdorff's process of coppering, 

189, 190 
Lunar caustic, 367 



MACHINE, alternate current, 62 
continuous current, 62 
first electro-magnetic, 20 
for gilding metallic wire and 
gauze, 245-247 
Machines, black-leading, 289, 290 
magneto- and dynamo-electric, 

59-74 
planing or shaving, types of, 298, 

299 
self-acting polishing, 161-163 



Magnesian stone, 24 
Magnet, artificial, 24 

phenomena exhibited by a, 25 
Magnetic field, 25, 60 
iron ore, 24 
meridian, 25 

needle, Oersted's discoveries in 
regard to the deflection of 
the, 19 
rule for determining the di- 
rection of the, to the con- 
ducting wire, 33 
poles, 24 
Magnetism, 24-26 

Ampere's theory of, 25 
and electricity, 24-43 
former explanation of, 25 
Magneto- and dynamo- electric ma- 
chines, 59-74 
electric machine, transition of 
the, to the dynamo, 
61 
Siemens & Halske's, 68, 

69 
what it is, 60 
Marble, 361 
Mass, unit of, 41 
Matrices, preparation of, in plastic 

materia], 285-289 
Mechanical treatment of the metallic 

articles, 102-119 
Medals and coins, metallic, taking 

casts from, 305 
Medium wheel, 108 
Meidinger element, 48 
Mercuric nitrate, 367 
Mercurous nitrate, 366, 367 
Mercury salts, poisoning by, 347 
Meriden Britannia Co. Works, silver- 
ing of Britannia or 
white metal, German 
silver or nickel arti- 
cles in the, 216, 217 
striking solution used in 
the, "21 8 
Meridian, magnetic, 25 
M6riten's process of giving iron a lus- 
trous black color, 325 
Metal and acid, regaining of the, from 

exhausted dipping baths, 124 
Metal, backing, composition of, 297 
white, or Britannia, silvering of, 
• 216, 217 
Metallic articles, removal of oxide 
from, 126 
treatment of the, 102-126 



396 



INDEX. 



Metallic- 
powders, metallization by, 309 
surface, to make a gal vano- plastic 
copy from a, 299, 300 
Metallization by metallic powders, 
309 
by the wet way, 307-309 
of glass, porcelain, clay, terra 
cotta, etc., 313 
Metals and fluids, production of elec- 
tricity by the contact of, 28 
coloring, patinizing, oxidizing, 

etc., of, 316-326 
conductivity of, 29 
electro- deposited, structure of, 
114, 115 
deposition of, noticed by 
Cruikshank, 19 
gold and silver, incrustations 

with, 226, 227 
production of electricity by the 

contact of various, 27, 28 
reduction of, without a battery, 

133, 134 
table of the melting-points of 
some, 378 
Molecules, Clausius's theory of, 38, 

39 
Monopotassic carbonate, 361 
Montgomery, Dr., introduction of 

gutta-percha for moulds, by, 21 
Mould, detaching the deposit from 

the, 296 
Moulding in gutta-percha, 286 
in plaster of Paris, 304-306 
in stearine, 288, 289 
in wax, 288, 289 
materials for, 302 
surfaces in relief and not under- 
cut, 303 
undercut reliefs and round plastic 
objects, 303, 304 
Moulds, black-leading of the, 289- 
292 
gelatine, 310, 311 
introduction of gutta-percha, for, 

21 
making the, conductive, 307- 

309 _ 
metallic alloys for the prepara- 
tion of, 304 
plaster-of- Paris, to render imper- 
vious to water, 306, 307 
preparation of, in plastic mate- 
rial, 285-289 
suspension of the, in the bath, 293 



Moulds — 

wiring the, 292 

Multipliers, galvanoscopes, or galvano- 
meters, 34 

Muriate or hydrochlorate of zinc, 355, 
356 

Muriatic acid, 349 

Murray, discovery of black-leading 
by, 21 



NATURE printing, 311 
Needles, coppering of, 191 
Negative and positive electricity, 27 

or object wire, 87 
Neutral line or neutral zone, 24 
Newmann's method of coloring zinc 

black, 324 
Newton and Weil's bronze baths, 199 
Nicholson and Carlisle, decomposi- 
tion of water by, 18 
Nickel alloys, deposits of, 17 7-179 
ammonium sulphate, 365 
and cobalt, deposition of, 135- 
181 
solutions, Warren's 154, 155 
anodes, 144-14 7 

reddish tinge of, 147 
bath, neutrality of a, 1 38 

without nickel salt, 144 
baths for certain purposes, 142, 
143 
formulas for, and preparation 

of, 138-144 
general remarks on, 136- 

138 
impracticability of insoluble 

anodes for, 145, 146 
recent formulas for, 143 
refreshing of, 157, 158 
surface of anodes for, 146, 

147 
testing the acidity and alka- 
linity of, 138 
the first requisite in prepar- 
ing, 136 
Boettger's observations on the 

deposition of, 21, 22 
bronze, 177 
carbonate, 362 
chloride, 356 
deposition of an alloy containing, 

177 
deposits, polishing of, 117, 158 
galvanoplastic operations in, 314, 
315 



INDEX. 



397 



Nickel — 

or German silver articles, silver- 
ing of, 217 
patent for the deposition of, 21 
properties of, 135 
recovery of, from old baths, 1 74, 

175 
salt, choice of, 136 

dissolution of, 131, 132 
silver (German silver), cleansing 

and silvering of, 217 
solutions, sensitiveness of in- 
dividuals to, 346 
stripping an old coat of, 155 
sulphate, 364, 365 
various colors upon, 319, 320 
very thick deposits of, 150 
Nickeled iron objects, immersion of 

in boiling linseed oil, 117 
Nickeling, 135-179 

bath, additions to the, 137, 138 
black, 268 

by contact and boiling, 175-177 
criteria for judging the correct 

progress of, 149, 150 
defective, 155, 156 

to improve, 175 
en masse of small and cheap ob- 
jects, 153-155 
flat and round objects, 151 
general rules for, 152, 153 
hard, baths for, 172, 173 
iron objects, nickel salts not to be 

used in, 13b, 137 
lamp feet of cast-zinc, 151 
of copper and brass sheets, 167, 

168 
of electrotypes, cliches, etc., 172- 

174 
of knife blades, sharp surgical 

instruments, etc., 171, 172 
of sheet-iron and sheet-steel, 168, 

169 
of tin-plate, 167, 168 
of wire and wire gauze, 169-171 
principal phenomena in, 156, 157 
remedy against the yellowish 

tone of, 155, 156 
salts, prepared, the active con- 
stituent of, 136 
sheet-zinc, 158-167 
solid, 150, 151 

suitable current-strength for, 148, 
149 
Niel or nieled silvering, 227, 228 
Niello, Corvin's, 312 



Nitrates, 366, 367 
Nitre, cubic, 366 
Nitre, spirit of, 349 
Nitric acid, 349 

table of the specific gravity 
and content of, 380 
Nitrous and hyponitric gases, poison- 
ing by, 347, 348 
Nobili's rings, 20, 266 
Noe's pile, 58 

Non-electrics, definition of, 26 
Norris and Johnson's brass bath, 197 
North and south poles, 25 



OBJECT and anode wires coupling, 
of the, with the resistance boards, 
voltmeter, shunt, and 
baths, 95-97 
insulation of, 92 
or negative wire, 87 
rods, connection of the, 89 
Objects, cleansing of the, 99, 100 
Oersted, Prof., discoveries of, 19 
Ohm, law of, 19, 30 

proposition deduced from the law 

of, 33 
the, 42 
Oil of vitriol, 348, 349 
Old (antique) silvering, 228 
Organic acids, salts of the, 368, 369 
substances, addition of, to silver 
baths, 208 
Orpiment, 354 
Over- nickeling 
Oxide, removal of, from metallic arti- 
cles, 126 
Oxidized silver, 228, 229 
Oxidizing, patinizing, coloring, etc., 
of metals, 316-326 



PACINOTTI'S ring conductor, 22, 
61 
Palladium baths, 257 
deposition of, 257 
properties of, 257 
Paracelsus, coating of metals by im- 
mersion known to, 1 7 
Paris Mint, method of browning cop- 
per in the, 317, 318 
Parkes's method of metallization, 308 
Paste, cold silvering with, 223 
Pastes, argentiferous, composition of, 

223 
Patina, bronze-like, on tin, 326 



398 



INDEX. 



Patina — 

definition of, 316 
genuine, imitation of, 318, 319 
Patinizing, coloring, oxidizing, etc., 
of metals, 316-326 
definition of, 316 
Pfanhauser's remedy against the yel- 
lowish tone of nickel, 155, 156 
Philipp's process of coating laces and 

tissues with copper, 311, 312 
Phosphates and pyrophosphates, 367, 

368 
Pickle, 90 

for copper and its alloys, and 

German silver, 120, 121 
for iron, 119 
for the production of a grained 

surface, 124, 125 
for zinc objects, 120 
preliminary, 120 
Pickles, acid, management of, 121 
Pickling, 119-125 

deadening by, 121, 122 

or dipping, 90 

plant for absorbing the vapors 

evolved in, 122-124 
the main points in, 122 
Pile, Noe's, 58 
Volta's, 18 
Pins, silvering of, 222, 223 
Pitchers, milk, gilding of, 239, 240 
Pixii's electrical machine, 20, 60 
Planing or shaving machines, tvpes 

of, 298, 299 
Plaster of Paris and its use for mould- 
ing, 304-306 
Plastic objects, round and undercut 

reliefs, moulding of, 303, 304 
Plates, copper printing, galvanoplastic 
copper baths for, 281 
finishing the, 297-299 
for the production of imitations 

of leather, 312, 313 
mounting of, 298 
Plating balance, 212-214 
Platinic chloride, 357 
Platinizing by contact, 256 
execution of, 255, 256 
Platinum baths, formulae for, prepa- 
ration and properties of, 
251-255 
management of, 255 
deposition of, 251-257 
deposits, burnishing of, 118 
properties of, 251 



Platinum — 

recovery of, from platinum solu- 
tions, 256, 257 
Platoso-ammonium chloride, prepara- 
tion of, 252 
Poisoning by chemicals and the anti- 
dotes, 346-348 
Polarization, definition and cause of, 

46 
Polarizing- or counter-current, 152, 

153 
Poles, magnetic, 24 

north and south, 25 
Polishing, 112-114 

and grinding rooms, arrangement 

of, 78 
disks, 112 
lathes, American double, 112, 

113 
machines, self-acting, 161-163 
materials, 114 
nickel deposits, 158 
of electro-plated objects, 1 1 7-1 1 9 
of nickeled zinc sheets, 167 
of silvered articles, 215, 216 
or grinding sheet zinc, 160, 161 
silver plate and silver, lathe for, 
337 
Poole, Moses, first use of thermo- 
electricity by, 22 
Porcelain, metallization of, 313 
Positive and negative electricity, 27 

or anode wire, 87 
Potash, 360, 361 
-alum, 363 
bicarbonate of, 361 
caustic, 351, 352 
element, Dun's, 54, 55 
white prussiate of, 358, 359 
yellow prussiate of, 360 
Potassium and sodium, discovery of, 
19 
production of the amal- 
gams of, 20 
bitartrate, 368 
carbonate, 360, 361 

table of the specific gravity 
and content of solutions 
of, 378 
cyanide, 358, 359 

amount of, for silver baths, 

202, 203 
as a pickle for brass, 121 
copper baths without, 185, 
186 



INDEX. 



399 



Potassium cyanide — 

determination of the propor- 
tion of silver to, in silver 
baths, 206 



poisoning by, 346, 347 
ferro-cyanide, 360 

preference of gold baths, pre- 
pared with, 232 
hydrate, 351, 352 
nitrate, 366 
sodium tartrate, 368 
sulphide, 353 
Potential, electrical, 28 

or electro-motive force, 42 
Powell, benzoic acid as an addition to 
nickel baths, recommended by, 137, 
138 
Power, consumption of, in the electro- 
lysis, 41 
or force, 42 
Press, hydraulic, 287, 288 

toggle, 286, 287 
Pretsch, the heliographic process in- 
vented by, 301, 302 
Primary or inductive current, 36 
Processes of electro- deposition, 127- 

134 
Prussiate of silver, 360 

of zinc, 359, 360 
Prussic acid, 349, 350 

poisoning by, 346, 347 
Puscher's method of coloring zinc 

black, 324 
Pyrophosphates and phosphates, 367, 
368 



Q 



UANTITY, 42 
coupling the elements for, 32 
of current, 30-33 



RAG, gilding with the, 248, 249 
Kain water, 127 
Ratsbane, 350, 351 
Rauber's, F., self-acting polishing 

machine, 161-163 
Recovery of nickel from old baths, 

174, 175 
Red brass, 191, 192 
gilding, 241 

sulphide of antimony, 354 
Reduction of metals without a bat- 
tery, 133, 134 



Refreshing nickel baths, 157, 158 

Regions of the lines of force, or mag- 
etic field, 60 

Reinbold's, H., formula for an alu- 
minium bath, 273 

Reliefs, undercut, and round plastic 
objects, moulding of, 303, 304 

Removal of grease, 125, 126 

Resinous or negative electricity, 27 

Resist, composition of, 225 

Resistance, 29, 42 

board, 82 

and galvanometer, arrange- 
rs 

ment of the, 84 
boards, voltmeter, shunt and 
baths, coupling of the, with the 
object and anode wires, 95-97 
essential or internal, 30 
non-essential or external, 30 
Rinsing and cleansing apparatuses, 

90, 91 
Rochelle salt, 368 

Rodconnections and binding posts, 336 
Rods, anode, connection of the, 89 
conducting, 88 

contrivance for protecting the, 90 
object, connection of the, 89 
Rogers, Wm., Manufacturing Co , of 
Hartford, Conn., 
amount of silver de- 
posited upon plated 
tableware by the, 
211 
methods for preparing 
work for plating in 
the, 217 
striking solution used 
in the, 218 
Rose-color gilding, 242 
Roseleur, brass bath according to, 
192, 193 
plating balance improved by, 
212-214 
Rouge mixture, 114 
Roughing wheel, 108 
Ruolz, de, bronze bath according to, 
199 
first deposition of metallic alloys, 

by, 22 
progress in the galvano- plastic art 
due to, 21 



s 



AL ammoniac, 354 

solution, table showing the 
specific gravity of, 381 



400 



INDEX. 



Salt, common, 354 
Glauber's, 362 
Rochelle, 368 
rock, 354 
Seignette, 368 
Saltpetre, 366 
Chile, 366 
Salts of the organic acids, 368, 369 
Salzede's bronze bath, 199 
Sand blast, use of the, 105, 106 
Sawdust box, 101, 117 

for drying the objects, 91 
Saw-table, the, 297 
Saxton and Clarke, improvements in 

the electrical machine by, 60, 61 
Scamoni, the heliographic process, 

improved by, 301, 302 
Schuckert, S., dynamo of, 23, 65, 66 
Schulz's patent for removing hydro- 
chloric acid from the pores of cop- 
pered articles, 188 
Scratch-brush, circular construction of 
a, 104, 105 
brushes, 337 

choice of, 115 

forms and treatment of, 102, 
103 
brushing, 102-105 

by hand, operation of, 115, 

116 
the deposits, 114-177 
Secondary or induced current, 36 
Seebeck, discovery by, 58 
Seignette salt, 368 
Shaving or planing machines, types 

of, 298, 299 
Shell or deposit, backing the, 296, 

297 
Shunt, construction of the, 95 

voltmeter, resistance boards, and 
baths, coupling of the, with 
the object and anode wires, 95- 
97 
Siemens, W., discovery by, 61, 62 

improvement in the electrical 
machine by, 61 
magneto-electric machine of, 23 
& Halske's dynamo, 23, 69 

magneto- electric machine, 
68, 69 
Silver, amount of, deposited upon 
plated table ware, 211 
and gold, galvanoplastic opera- 
tions in, 315, 316 
deposits, burnishing of, 118 
anodes, 202-209 



Silver — 

articles, stripping the gold from, 

249, 250 
bath, wires for suspending objects 

in the, 210 
baths, addition of organic sub- 
stances to, 208 
agitation of the objects in 

the, 207, 208 
amount of potassium cyanide 

for, 202, 203 
augmentation of, 205 
current-strength for, 203 
determination of the actual 
content of silver in, 207 
of the proportion of 
silver to potassium 
cyanide in, 206 
formula? for, preparation and 

properties of, 200-202 
gradual thickening of, 205, 

206 
recovery of silver from old, 

230, 231 
treatment of, 202-209 
calculating the weight of the de- 
posit of, from the density of 
current, 215 
chloride, 356, 357 

or silver cyanide, choice of 

for baths, 200, 201 
preparation of a silver bath 

with, 201 
proper treatment of baths 
made with, 205, 206 
coloring of, 326 

control of the weight of the de- 
posit of, 211-214 
cyanide, 360 

or silver chloride, choice 
of, for silver baths, 200, 
201 
preparation of a silver bath 
with, 201, 202 
dead white coating of, 215 
deposition of, 200-231 
determination of the actual con- 
tent of, in silver baths, 
207 
of the proportion of, to potas- 
sium cyanide in silver 
baths, 206 
first electro-coating of, with cop- 
per, 18 
gold and other metals, incrusta- 
tions, with, 226, 227 



INDEX. 



401 



Silver- — 

heavy coating of, on the convex 
surfaces of spoons and 
forks, 218 
electro-deposit of, baths for, 
200-202 
hydrocyanate of, 360 
nitrate, 367 
oxidized, 228, 229 
plate and silver, lathe for polish- 
ing, 337 
powder, mode of making, 224 
properties of, 200 
prussiate of, 360 
recovery of, from old silver baths, 

230, 231 
solder, 377 
Silvered and gilt black-lead, 291, 292 
articles, burnishing of, 215, 216 
dissolving silver from, 229, 

230 
polishing of, 215, 216 
yellow color upon, 229 
Silvering by contact, by immersion, 
and cold silvering with paste, 
219-223 
by weight, 209-216 

baths for, 200-202 
cold, with paste, 223 
electro-deposited, determination 

of, 230 
execution of, 209-219 
nielled, or niel, 227, 228 
of copper wire, 226 
old (antique), 228 
ordinary, 216-219 
remedy against the yellow tone 
of, 208, 209 
Similor, 191, 192 
Sine galvanometer, 34 
Siphons, 344 
Skates, removal of grease from, 125, 

126 
Slinging wires, 334 
Smee, Alfred, discoveries by, 21 
element of, 46, 47 
experiments on copper by, 273, 
274 
Soda, caustic, 351, 352 

washing, 361 
Sodium and potassium, discovery of, 
19 
production of the amal- 
gams of, 20 
bicarbonate, 361 
bisulphite, 366 
26 



Sodium — 

carbonate, 361 

chloride, 354 

citrate, 369 

hydrate, 351, 352 

nitrate, 366 

phosphate, 367, 368 

pyrophosphate, 368 

sulphate, 362 

sulphide, preparation of solution 

of, 220, 221 
sulphite, 365, 366 
Soft solder, 377 

Solders and alloys, table showing the 
composition of the most usual, 
3 75-378 
table of, 37 7, 378 
Solubility, table showing the, of vari- 
ous substances, 375 
Sources of current, 44-74 
South and north poles, 25 
Spaeth, J. W., machine for gilding 
metallic wire and gauze constructed 
by, 245-247 
Spencer, T., claim by, 20 
Spirit of nitre, 349 
Spirits of hartshorn, 352 
Spoons and forks, heavy coating of 
silver on the convex surfaces of, 
218 
Spring water, 127 
Stannic chloride, 355 
Stannous chloride, 355 
Stearine, moulding in, 288, 289 
Steel and iron articles, copper baths 
for, 182-184 
grinding of, 111 
tinning solution for, 
261 
most suitable current- 
density for nickeling, 
150 
objects, production of a 
thin film of cop- 
per on, 190, 191 
removal of oxide 
from, 126, 
sheet, nickeling of, 168, 
169 
baths, formulas for, preparation 

and properties of, 267 
(cutlery), cleansing and silvering 

of, 217 
pens, coppering of, 191 
Steeling, 266-269 
by contact, 269 



402 



INDEX. 



Steeling — 

execution of, 269 
Stibium sulfuratum aurantiacum, 354 

nigrum, 353 
Stirring rods, 339, 340 
Stoehrer's battery, 57 
Stolba's method of tinning, 262 

process of nickeling by contact, 
175, 176 
Stoneware vats, 88 
Stopping off, 218, 219 

varnish, 218 
Striking solutions, 218 
Stripping an old coat of nickel, 155 
the cobalt from cobalted copper 

plates, experiment in, 180 
gold from gilded articles, 249, 250 
silver from silvered articles, 229, 
230 
Substances, various, table showing 

the solubility of, 375 
Sugar of lead, 369 
Sulphates and sulphites, 362-366 
Sulphide, arsenious, 354 

ferric, 354 
Sulphites and sulphates, 362-366 
Sulphur combinations, 352-354 
Sulphur, liver of, 353 
Sulphuretted hydrogen, 352, 353 

poisoning by, 34 7 
Sulphuric acid, 348, 349 

solutions, table showing the 
specific electrical resist- 
ances of different, 373 
table showing the specific 
gravity of, 379 
Sulphurous acid, poisoning by, 347, 

348 
Sulphydric acid, 352, 353 
Surgical instruments, sharp, and knife 
blades, nickeling of, 171, 
172 
to protect wooden handles 
of, 313 
Switch board, 82 
Symer's theory of electricity, 27 



TABLE for freeing the articles from 
grease, 100, 101 
Tables, useful, 370-382 
Tangent galvanometer, 34 
Tartar emetic, 369 
Teeth, neutralizing the action of acids 

upon the enamel of the, 345 
Temperatures, high, table of, 378 



Tension, coupling the elements for, 32 

series of, 28 
Terchloride of gold, 357 
Terra-cotta, metallization of, 313 
Thermo-electricity, first use of, 22 
pile, Clamond's, 58, 59 
piles, 57-59 
Thermometers, to surround the mer- 
cury vessels of, with a thick copper 
deposit, 313 
Thumb, gilding with the, 248, 249 
Time, unit of, 41 

Tin baths, formulae for, preparation 
and properties of, 258, 259 
management of, 259, 260 
chlorides, 355 
coloring of, 3i'6 
deposition of, J57-262 

of an alloy of zinc with, 265 
deposits, polishing of, 117, 118 
moir6 metallique on, 258 
plate, nickeling of, 167, 168 
properties of, 257, 258 
salt, 355 
Tinning by contact and boiling, 260- 
262 
execution of, 260 
Tissues and laces, process of coating, 

with copper, 311, 312 
Toggle press, 286, 287 
Tombac, 191, 192 
deposits of, 200 
pickling of, 1 20 
removal of oxide from, 126 
Transmission, location of the, 78, 79 
Treatment of the metallic articles, 

102-126 
Trough battery, 1 8, 44 
Tub for freeing the objects from 

grease, 90 
Tumbling drum or box, 106, 107 
Twaddell's hydrometer, 341, 342 



UNITS, electric, 41-43 
Urquhart's method of coloring 
brass black, 320 
plan for recovering nickel 
from old solutions, 174, 
175 
Useful tables, 370-382 



VAPORS, plant for absorbing the, 
evolved in pickling, 122-124 
Varnish, removal of, 329 



INDEX. 



403 



Varnish — 

stopping off, 218 
very resisting, 219 
Varnishes, materials employed for, 

329 
Varrentrapp's steel bath, 267 
Yases, busts, etc., galvanoplastic re- 
production of, 302-307 
Vats, 87, 88, 333, 334 
for heating baths, 88 
for silver baths, 202 
stoneware, 88 

wooden, mixtures for coating, 87 
Ventilation and light of workrooms, 

75, 76 
Verdigris, 369 

Vienna lime, constitution of, 109 
Vitreous or positive electricity, 27 
Vitriol, blue, 364 

pure crystallized, table of the 
contents of, 277 
green, 363, 364 
white, 364 
Volt, the, 42 
Volta, Alexander, discoveries by, 17, 

18 
Voltaic pile, 18, 44 
Voltameter, experiments with the, 39, 

40 
Voltmeter, 93 

resistance boards, shunt, and 
baths, coupling of the, with 
the object and anode wire, 95- 
97 



WAHL, Dr. W. H., directions for 
preparing platinum baths by, 
252-255 
Walenn's copper bath, 186 
Warren's cobalt solution, 180 

nickel and cobalt solutions, 154, 
155 
Washing soda, 361 

Watch parts, grained, gilding of, 226 
Water, first decomposition of, 18 

importance of the constitution of, 

127 
reservoirs, 101 
supply of, 77 
Watt, method for obtaining a deposit 
of German silver recommended 
by, 178, 179 
and Elmore's mixture for strip- 
ping the old coat of nickel, 155 
the, 43 



Wax, moulding in, 288, 289 
Weight of the deposit of silver, con- 
trol of the, 211-214 
silvering by, 209-216 
Weil and Newton's bronze baths, 199 
Weil's copper bath, 186 

method of zincking, 264, 265 
Weiler, Lazere, conductivity of metals 

according to, 29 
Well water, 127 

Weston, boric acid as an addition to 
nickel baths recommended bv, 
137, 138 
dynamo, 69, 70 
Wheatstone, Sir C, discovery by, 61, 
62 
magneto-electric machine of, 23 
Wheel, fine, 108 
medium, 108 
roughing, 108 
White metal or Britannia, silvering 
of, 216, 217 
prussiate of potash, 358, 359 
vitriol, 364 
Whiting, 361 

Wire and wire-gauze, gilding of, 245- 
247 
nickeling of, 169-171 
carriers, form of, 92 
copper, silvering of, 226 
gauges, table showing actual dia- 
meters in decimal parts of an 
inch corresponding to the num- 
ber of various, 382 
negative or object, 87 
positive or anode, 87 
Wire-hooks, frame for the reception 

of, 101 
Wires, action of two electrified on 
each other, 35 
best, for conducting the current, 

87 
conducting, 334-336 

calculating the thickness of 
the, for dynamos, 101 
for suspending objects in the 

silver bath, 210 
object and anode, coupling of 
the, with the resistance boards, 
voltmeter, shunt, and baths, 
95-97 
object and anode, insulation of, 92 
slinging, 334 
AViring the moulds, 292 
Wollaston, electro-coating of silver 
with copper by, 18 



404 



INDEX. 



Wood, floor of, 77 

to coat with a galvano-plastie de- 
posit of copper, 313 
Wooden handles of surgical instru- 
ments, to protect, 313 
vats, mixtures for coating, 87 
Work, 42 
Work-room, size of, 7 7 

light and ventilation of, 75, 76 
Work-shop, hygienic rules for the, 

345-348 
Wright, first employment of alkaline 

cyanides, by, 21 
Wrought-iron, brass bath for, 197 

and cast-iron articles, solution for 
coating with bronze, 198, 199 
iron and cast-iron objects, pick- 
ling of, 119, 120 



YELLOW brass, 191, 192 
Yellow prussiate of potash, 360 



ZAPON, a dipping lacquer, 327, 
328 
Zinc alloys, production of, 265 

amalgamation of the, of elements, 

45, 46 
articles, bath for coppering, 184, 
185 
slightly coppered, nickel bath 
for, 142, 143 
baths, formulas, preparation and 

properties of, 262-264 
brass bath for, 196 
bronzing on, 324, 325 
butter of, 355, 356 
carbonate, 362 

cast, nickeling lamp feet of, 151 
castings, grinding of, 111, 112 

nickel bath for, 141 
chloride, 355, 356 

and ammonium chloride, 356 



Zinc — 

coppering of, by dipping, 190 
cyanide, 359, 360 
deposition of, 262-265 

of an alloy of, with tin, 265 
hydrochlorate or muriate of, 355, 

356 
hydrocyanate of, 359, 360 
objects, deadening of, 243 
pickling of, 120 
small, bath for coppering, 
185 
properties of, 262 
prussiate of, 359, 360 
sheet and castings, dark nickeling 

upon, 143 
sheets, anodes for nickeling, 166 
appearance of black streaks 
and stains in nickeling, 
166, 167 
brassing of, 164, 165 
construction of bobs for 

polishing, 159, 160 
coppering of, 1 65 
current-strength for nickel- 
ing, 165, 166 
freeing from grease, 163, 164 
nickeled, polishing of, 167 
nickeling of, 158-167 
polishing or grinding of, 160, 
161 
sulphate, 364 

to coat brass and copper with, 
264 
Zincking, execution of, 264 
iron by contact, 264 
Weil's method of, 264, 265 
Zone, neutral, 24 
Zozimus, simple reduction of metals, 

known to, 1 7 
Zucker & Levett Chemical Co., of 
New York, the American " Giant" 
dynamo-machine, manufactured by 
the, 332, 333 



The New H. & V. W. Dynamo 




The Hanson & Van Winkle Company 



ESTABLISHED 1820 

81 Liberty Street 

NEW YORK 



Manufactory and Offices 

219 and 221 Market Street 

NEWARK, N. J. 



INCORPORATED 1891 

35 and 37 South Canal Street 

CHICAGO, ILL. 



J. E. HARTLEY & CO., Sole European Agents, 
St. Paul's Square, Birmingham. 

We are now ready to send out five sizes of our new and improved Dynamo, 
which we are safe in guaranteeing thirty per cent, more powerful than any other 
machine sold at same price. 

The following are some of the many advantages offered : 

The Field Magnets have wrought iron in them, vastly superior to cast iron. 

The Magnets have a round core, which for a given amount of wire is much 
more powerful. 

They have a very short magnetic circuit — a very good point. 

The Commutator is easily taken off, so as to renew the segments, which are 
made of tempered copper, and are very durable. 

The Armature and working parts are away from the base, and are protected 
fully from dirt. 

The Field Magnets are wound on bobbins and are easily replaced, no return 
of machine and expensive repairs ever being required. 

Clean lubrication, requiring attention but once a week. No oil to get in 
Armature like all other Dynamos. 

Appearance : Without sacrificing the electrical efficiency of the machine, it is 
the most attractive in the market, and consequently will receive more care from 
those in charge. 



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Being the very first to undertake this branch ot business in this country, and introduce the 
first Dynamo-Electric Machines and the popular use of Nickel-plating, etc., we feel like taking 
to ourselves a little of the credit for the vast strides that have been made in this country within 
the last* fifteen years in the manufacture of Metal Goods, in which we now so far excel in quality 
and price all European manufacturers. 

In order to maintain our trade, we are constantly looking out for all improvements and 
processes relating to this business. We particularly call attention to improvements and great 
reduction in price of Dynamo-Electric Machines, and Nickel-Plating Outfits, Dynamo-Machines 
for Electro-Refining ; to the new Lacquers introduced by us, and used by all the largest manu- 
facturers of Metal Goods ; to the various new Polishing Materials, Tripoli, etc., introduced by us : 
and recent improvements in the manufacture and reduction in price of Fine Rouges, Cyanide 01 
Potash, XXX Lye, and the various chemicals used by the trade ; and to the new Wheels, Prepared 
Buffs, Black Nickel Solution and Anodes, 14-karat Gold-Plating Outfits, etc. 

Nickel 
Plating 
Outfits 

From $20 upward 

And for Silver, 

Gold, etc. 





Our No. 3 Lathe 

Self-Oiling Buffing Lathe 

These Lathes are made in the best manner, with Steel Spindles, Wide, Hard Metal 
Bearings, and designed for quick speeds. They stand 10 inches high, and have Spindles 
3 feet long, i 1 /. inches in diameter ; weight, 63 lbs. They are regularly made with Collars 
on both ends of Spindle. The pulley is 4 inches diameter, 3^ inch face. The Spindle is 
1 inch diameter between the collars. Unless otherwise stated, orders will be filled as shown. 

We can furnish these with fast and loose pulleys. We will furnish detachable taper 
end without extra charge. This is one of our standard Lathes. In large numbers will 
make special price. Price, $16.00. 




The New No. 5 Lathe 

Self-Oiling 

This Lathe is unequaled by anything in the market for running wood or leather 
wheels, or large muslin buffs at a high speed. 

Unlike the old-style "single upright" Lathes, there is no vibration. 

Height, 22 inches to Spindle ; Steel Spindle, 38 inches long, 1% inches diameter ; 
bearings, 7 inches wide ; fast and loose pulleys, each 4x4; weight, 209 lbs. 

Price, $25.00. In large numbers we make special discount. 

Compare our prices, weights and construction with other makers. 

We are the largest manufacturers of Rouge and all Polishing Materials, Vienna 
Lime, Cyanide of Potash, etc. 




No. 200 

Complete Box of Polishing Tools and Powders for small work $3.00 

Polishing Outfits for all purposes. We are the largest manufacturers of fine Steel and Brass 
Wire Scratch Brushes, Platers' Brushes, Bristle, Tampico, etc. 

PATENT KRISTALINE— A Dip Lacquer 

For Protecting the Surface of Metals of all kinds with an Indestructible, Glass-like Coating 
or Transparent Enamel, that will resist Acids, Alcohol, Oils, Water, etc., and so hard as not to 
scratch like ordinary Lacquer. 

It is used on the most highly polished metals without affecting finish or color, as well as on 
the delicate shades of color produced by various metallic solutions, oxidizing, etc. 

We furnish everything. 
The Hanson & Van Winkle Co., Newark, N. J., U. S. A. 



C.A.T-A.XOGrTTE 

OF 

practical and Scientific Boo^ 

PUBLISHED BY 

Henry Carey Baird & Co, 



INDUSTRIAL PUBLISHERS, BOOKSELLERS AND IMPORTERS. 

810 Walnut Street, Philadelphia. 



MS* Any of the Books comprised in this Catalogue will he sent by mail, free erf 
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j9®* A Descriptive Catalogue, 84 pages, 8vo., will be sent free and free of postage, 
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J8SF- Where not otherwise stated, all of the Books in this Catalogue are bound 
in muslin. 



AMATEUR MECHANICS' WORKSHOP: 

A treatise containing plain and concise directions for the manipula- 
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Soldering and Carpentry. By the author of the " Lathe and Its 
Uses." Seventh edition. Illustrated. 8vo. . . . $3.00 

ANDRES.— A Practical Treatise on the Fabrication of Volatile 
and Fat Varnishes, Lacquers, Siccatives and Sealing 
Waxes. 
From the German of Erwin Andres, Manufacturer of Varnishes 
and Lacquers. With additions on the Manufacture and Application 
of Varnishes, Stains for Wood, Horn, Ivory, Bone and Leather. 
From the German of Dr. Emil Winckler and Louis E. Andes. 
The whole translated and edited by William T. Brannt. With 1 1 
illustrations. i2mo. . $2-50 

ARLOT.— A Complete Guide for Coach Painters : ( 

Translated from the French of M. Arlot, Coach Painter; for 
eleven years Foreman of Painting to M. Eherler, Coach Maker, 
Paris. By A. A. Fesquet, Chemist and Engineer. To which is 
added an Appendix, containing Information respecting the Materials 
and the Practice of Coach and Car Painting and Varnishing in the 
United States and Great Britain. i2mo. . . . $1.25 

(0 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 



ARMENGAUD, AMOROUX, AND JOHNSON.— The Practi- 
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Forming a Complete Course of Mechanical Engineering and Archi- 
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Prof, of Design in the Conservatoire of Arts and Industry, Paris, and 
MM. Armengaud the younger, and Amcroux, Civil Engineers. Re- 
written and arranged with additional matter and plates, selections from 
and examples of the most useful and generally employed mechanism 
of the day. By William Johnson, Assoc. Inst. C. E. Illustrated 
by fifty folio steel plates, and fifty wood-cuts. A new edition, 4to M 

half morocco $10.00 

ARMSTRONG.— The Construction and Management of Steam 
Boilers : 
By R. Armstrong, C. E. With an Appendix by Robert Mallet, 
C. E., F. R. S. Seventh Edition. Illustrated. 1 vol. i2mo. 75 

ARROWSMITH.— Paper- Hanger's Companion : 

A Treatise in which the Practical Operations of the Trade are 
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various Cements and Pastes Adapted to the Several Purposes oi 
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ASHTON. — The Theory and Practice of the Art of Designing 
Fancy Cotton and Woollen Cloths from Sample : 
Giving full instructions for reducing drafts, as well as the methods of 
spooling and making out harness for cross drafts and finding any re- 
quired reed; with calculations and tables of yarn. By Frederic T. 
Ashton, Designer, West Pittsfield, Mass. With fifty-two illustrations. 
One vol. folio $6.co 

AUERBACH— CROOKES.— Anthracen : 

Its Constitution, Properties, Manufacture and Derivatives, including 
Artificial Alizarin, Anthrapurpurin, etc., with their applications in 
Dyeing and Printing. By G. Auerbach. Translated and edited 
fiom the revised manuscript of the Author, by Wm. Crookes, F. R. 
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BAIRD.— Miscellaneous Papers on Economic Questions. 
By Henry Carey Baird. {In preparation.) 

BAIRD.— The American Cotton Spinner, and Manager's and 
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A Practical Treatise on Cotton Spinning ; giving the Dimensions and 
Speed of Machinery, Draught and Twist Calculations, etc.; with 
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for making changes in the sizes and numbers of Roving and Yarn. 
Compiled from the papers of the late Robert H. Baird. i2mo. 

#i.5 c 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 



BAIRD.— Standard Wages Computing Tables : 

An Improvement in all former Methods of Computation, ro arranged 
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BAKER. — Long-Span Railway Bridges : 
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BAKER.— The Mathematical Theory of the Steam-Engine : 
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BARLOW.— The History and Principles of Weaving, by 
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Reprinted, with Considerable Additions, from " Engineering," with 
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BARR. — A Practical Treatise on the Combustion of Coal: 
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BARR. — A Practical Treatise on High Pressure Steam Boilers : 
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204 Illustrations. 8vo . . $3.00 

BAUERMAN. — A Treatise on the Metallurgy of Iron: 

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and Steel, etc., etc. By H. Bauerman, F. G. S., Associate of the 
Royal School of Mines. Fifth Edition, Revised and Enlarged. 
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BAYLES.— House Drainage and Water Service : 

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BEANS.— A Treatise on Railway Curves and Location of 
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BECKETT.— A Rudimentary Treatise on Clocks, and Watches 

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By Sir Edmund Beckett, Bart., LL. D., Q. C. F. R. A. S. With 

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I2mo #2.25 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 



BELL. — Carpentry Made Easy : 

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BEMROSE. — Fret-Cutting and Perforated Carving: 

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BEMROSE. — Manual of Buhl-work and Marquetry: 

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BEMROSE.— Manual of Wood Carving: 

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BILLINGS.— Tobacco : 

Its History, Variety, Culture, Manufacture, Commerce, and Various 
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BIRD. — The American Practical Dyers' Companion: 

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BLINN. — A Practical Workshop Companion for Tin, Sheet- 
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HENRY CAREY BAIRD & CO.'S CATALOGUE. 



SOOTH.— Marble Worker's Manual: 

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With an Appendix concerning American Marbles. i2mo., cloth $1.50 
BOOTH and MORFIT.— The Encyclopaedia of Chemistry, 
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Embracing its application to the Arts, Metallurgy, Mineralogy, 
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BRAM WELL.— The Wool Carder's Vade-Mecum* 

A Complete Manual of the Art of Carding Textile Fabrics. By W, 
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BRANNT.— A Practical Treatise on Animal and Vegetable 
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Comprising both Fixed and Volatile Oils, their Physical and Chemi- 
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BRANNT.— A Practical Treatise on the Manufacture of Soap 
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Based upon the most Recent Experiences in the Practice and Science ; 
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BRANNT.— A Practical Treatise on the Raw Materials and the 
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Edited chiefly from the German of Dr. K. Stammer, I)r. F. Eisner, 
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engravings. 121110. ....... $2. SO 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 



SRANNT— WAHL.- The Techno- Chemical Receipt Book: 

Containing several thousand Receipts covering the latest, most aa 
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their Practical Application in the Arts and the Industries. Edited 
chiefly from the German of Drs. Winckler, Eisner, Heintze, Mier* 
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i2mo. 495 page- . . • . $2 00 

EROWN. — Five Hundred and Seven Mechanical Movements. 
Embracing all those which are most important in Dynamics, Hy- 
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Gearing, Presses, Horology and Miscellaneous Machinery; and in- 
cluding many movements never before published, and several of 
which have only recently come into use. By Henry T. Brown. 
i2mo $1.00 

BUCKM ASTER.— The Elements of Mechanical Physics : 
By J. C. Buckmaster. Illustrated with numerous engravings. 
i2mo $1.50 

BULLOCK.— The American Cottage Builder : 

A Series of Designs, Plans and Specifications, from $200 to $20,000, 
for Homes for the People ; together with Warming, Ventilation, 
Drainage, Painting and Landscape Gardening. By John Bullock, 
Architect and Editor of " The Rudiments of Architecture and 
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BULLOCK.— The Rudiments of Architecture and Building: 
For the use of Architects, Builders, Draughtsmen, Machinists, En- 
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American Cottage Builder." Illustrated by 250 Engravings. 8vo. $3.$o 

BURGH. — Practical Rules for the Proportions of Modern 
Engines and Boilers for Land and Marine Purposes. 
By N. P. Burgh, Engineer. i2mo. . . . . $1.50 

BYLES. — Sophisms of Free Trade and Popular Political 

Economy Examined. 

By a Barrister (Sir John Barnard Byles, Judge of Common 

Pleas). From the Ninth English Edition, as published by the 

Manchester Reciprocity Association. i2mo. . . . $1.25 

BOWMAN.— The Structure of the Wool Fibre in its Relation 
to the Use of Wool for Technical Purposes : 
Being the substance, with additions, of Five Lectures, delivered at 
the request of the Council, to the members of the Bradford Technical 
College, and the Society of Dyers and Coloiists. By F. H. Bow- 
man, D. Sc, F. R. S. E., F. L. S. Illustrated by 32 engravings. 
8vo. $6,50 

f^YRNE. — Hand-Book for the Artisan, Mechanic, and Engi- 
neer: 
Comprising the Grinding and Sharpening of Cutting Tools, Abrasive 
Processes, Lapidary Work, Gem and Glass Engraving, Varnishing 
aod Lackering, Apparatus, Materials and Processes for Grinding and 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 



Polishing, etc. By Oliver Byrne. Illustrated by 185 wood en- 
gravings. 8vo. #5.00 

BYRNE.— Pocket-Book for Railroad and Civil Engineers : 

Containing New, Exact and Concise Methods for Laying out Railroad 
Curves, Switches, Frog Angles and Crossings ; the Staking out of 
work ; Levelling ; the Calculation of Cuttings ; Embankments ; Earth- 
work, etc. By Oliver Byrne. i8mo., full bound, pocket-book 
form $1-75 

BYRNE.— The Practical Metal-Worker's Assistant : 

Comprising Metallurgic Chemistry; the Arts of Working all Metals 
and Alloys ; Forging of Iron and Steel; Hardening and Tempering; 
Melting and Mixing; Casting and Founding ; Works in Sheet Metal; 
the Processes Dependent on the Ductility of the Metals; Soldering*, 
and the most Improved Processes and Tools employed by Metal- 
workers. With the Application of the Art of Electro-Metallurgy to 
Manufacturing Processes ; collected from Original Sources, and from 
the works of Holtzapffel, Bergeron, Leupold, Plumier, Napier, 
Scoffern, Clay, Fairbairn and others. By Oliver Byrne. A new, 
revised and improved edition, to which is added an Appendix, con- 
taining The Manufacture of Russian Sheet-Iron. By John Percy, 
M. D., F. R. S. The Manufacture of Malleable Iron Castings, and 
Improvements in Bessemer Steel. By A. A. Fesquet, Chemist and 
Engineer. With over Six Hundred Engravings, Illustrating every 
Branch of the Subject. 8vo $5-00 

BYRNE.— The Practical Model Calculator: 

For the Engineer, Mechanic, Manufacturer of Engine Work, Nava» 
Architect, Miner and Millwright. By Oliver Byrne. 8vo., nearly 
600 pages ......... $4-5* 

CABINET MAKER'S ALBUM OF FURNITURE: 

Comprising a Collection of Designs for various Styles of Furniture. 
Illustrated by Forty-eight Large and Beautifully Engraved Plates. 
Oblong, 8vo $3.50 

CALLINGHAM.— Sign Writing and Glass Embossing: 

A Complete Practical Illustrated Manual of the Art. By James 
Callingham. i2ino. $1.50 

CAMPIN.— A Practical Treatise on Mechanical Engineering: 
Comprising Metallurgy, Moulding, Casting, Forging, Tools, Work, 
shop Machinery, Mechanical Manipulation, Manufacture of Steam* 
Engines, etc. With an Appendix on the Analysis of Iron and Iron 
Ores. By Fpancis Campin, C. E. To which are added, Observations 
on the Construction of Steam Boilers, and Remarks upon Furnaces 
used for Smoke Prevention ; with a Chapter on Explosions. By R. 
Armstrong, C. E., and John Bourne. Rules for Calculating the 
Change Wheels for Screws on a Turning Lathe, and for a Wheel, 
cutting Machine. By J. La Nicca. Management of Steel, Includ- 
ing Forging, Hardening, Tempering, Annealing, Shrinking and 
Expansion ; and the Case-hardening of Iron. By G. Ede. 8vo. 
Illustrated with twenty-nine plates and 100 wood engravings $5.00 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 



CAREY.— A Memoir of Henry C. Carey. 

By Dr. Wm. Elder, With a portrait. 8vo., cloth . . ^"J 

CAREY.— The Works of Henry C. Carey : 

Harmony of Interests : Agricultural, Manufacturing and Commer* 

cial. 8vo. . . $l.$Q 

Manual of Social Science. Condensed from Carey's " Principles 
of Social Science." By Kate McKean. i vol. i2mo. . #2.25 
Miscellaneous Works. With a Portrait. 2 vols. 8vo. $6.00 

Past, Present and Future. 8vo #2.50 

Principles of Social Science. 3 volumes, 8vo. . . $10.00 
The Slave-Trade, Domestic and Foreign; Why it Exists, and 
How it may be Extinguished (1853). 8vo. . . , $2.00 

The Unity of Law : As Exhibited in the Relations of Physical, 
Social, Mental and Moral Science (1872). 8vo. . . $3.50 

CLARK. — Tramways, their Construction and Working : 

Embracing a Comprehensive History of the System. With an ex^ 
haustive analysis of the various modes of traction, including horse- 
power, steam, heated water and compressed air; a description of the 
varieties of Rolling stock, and ample details of cost and working ex- 
penses. By D. Kinnear Clark. Illustrated by over 200 wood 
engravings, and thirteen folding plates. 2 vols. 8vo. . #12.50 

COLBURN.— The Locomotive Engine: 

Including a Description of its Structure, Rules for Estimating its 
Capabilities, and Practical Observations on its Construction and Man- 
agement. By Zerah Colburn. Illustrated. i2mo. . $1.00 

COLLENS.— The Eden of Labor; or, the Christian Utopia. 
By T. Wharton Collens, author of " Humanics," "The History 
of Charity," etc. i2mo. Paper cover, $1.00; Cloth . $1.25 

COOLEY.— A Complete Practical Treatise on Perfumery: 
Being a Hand-book of Perfumes, Cosmetics and other Toilet Articles. 
With a Comprehensive Collection of Formulae. By Arnold J. 
Cooley. i2mo • . #1.50 

COOPER.— A Treatise on the use of Belting for the Trans- 
mission of Power. 
With numerous illustrations of approved and actual methods of ar« 

' ranging Main Driving and Quarter Twist Belts, and of Belt Fasten- 
ings. Examples and Rules in great number for exhibiting and cal- 
culating the size and driving power of Belts. Plain, Particular and 
Practical Directions for the Treatment, Care and Management of 
Belts. Descriptions of many varieties of Beltings, together with 
chapters on the Transmission of Power by Ropes; by Iron and 
Wood Frictional Gearing; on the Strength of Belting Leather; and 
on the Experimental Investigations of Morin, Briggs, and others. By 
John H. Cooper, M. E. 8vo #3-50 

CRAIK. — The Practical American Millwright and M^ler. 

1' By David Craik, Millwright. Illustrated by numerous wood en- 
gravings and two folding plates. 8vo. ...» $5.00 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 



CREW. — A Practical Treatise on Petroleum : 

Comprising its Origin, Geology, Geographical Distribution, History, 
Chemistry, Mining, Technology, Uses and Transportation. Together 
with a Description of Gas Wells, the Application of Gas as Fuel, etc. 
By Benjamin J. Crew. With an Appendix on the Product and 
Exhaustion of the Oil Regions, and the Geology of Natural Gas in 
Pennsylvania and New York. By Charles A. Ashburner, M. S._ 
Geologist in Charge Pennsylvania Survey, Philadelphia. Illustrated 
by 70 engravings. 8vo. 508 pages .... $5.00 

CROSS. — The Cotton Yarn Spinner : 

Showing how the Preparation should be arranged for Different 
Counts of Yarns by a System more uniform than has hitherto been 
practiced; by having a Standard Schedule from which we make all 
our Changes. By Richard Cross. 122 pp. i2mo. . 75 

CRISTIANI. — A Technical Treatise on Soap and Candles: 
With a Glance at the Industry of Fats and Oils. By R. S. Cris- 
TIANI, Chemist. Author of "Perfumery and Kindred Arts." Illus- 
trated by 176 engravings. 581 pages, 8vo. . . . $12.50 

CRISTIANI.— Perfumery and Kindred Arts: 
A Comprehensive Treatise on Perfumery, containing a History of 
Perfumes from the remotest ages to the present time. A complete 
detailed description of the various Materials and Apparatus used in 
the Perfumer's Art, with thorough Praciical Instruction and careful 
Formulae, and advice for the fabrication of all known preparations of 
the day, including Essences, Tinctures, Extracts, Spirits, Waters, 
Vinegars, Pomades, Powders, Paints, Oils, Emulsions, Cosmetics, 
Infusions, Pastilles, Tooth Powders and Washes, Cachous, Hair Dyes, 
Sachets, Essential Oils, Flavoring Extracts, etc. ; and full details for 
making and manipulating Fancy Toilet Soaps, Shaving Creams, etc., 
by new and improved methods. With an Appendix giving hints and 
advice for making and fermenting Domestic Wines, Cordials, Liquors, 
Candies, Jellies, Syrups, Colors, etc., and for Perfuming and Flavor- 
ing Segars, Snuff and Tobacco, and Miscellaneous Receipts foi 
various useful Analogous Articles. By R. S. CRISTIANI, Con- 
sulting Chemist and Perfumer, Philadelphia. 8vo. . . $10.00 

DAVIDSON.— A Practical Manual of House Painting, Grain- 
ing, Marbling, and Sign- Writing : 
Containing full information on the processes of House Painting in 
Oil and Distemper, the Formation of Letters and Practice of Sign- 
Writing, the Principles of Decorative Art, a Course of Elementary 
Drawing for House Painters, Writers, etc., and a Collection of Useful 
Receipts. With nine colored illustrations of Woods and Marbles, 
aad numerous wood engravings. By Ellis A. Davidson. i2mo. 

$3.00 

DAVIES.— A Treatise on Earthy and Other Minerals and 
Mining : 
By D. C. Davies, F. G. S., Mining Engineer, etc. Illustrated by 
76 Engravings. i2mo $5 .00 



to HENRY CAREY BAIRD & CCVS CATALOGUE. 

DAVIES.— A Treatise on Metalliferous Minerals and Mining: 
By D. C. Davies, F. G. S. r Mining Engineer, Examiner of Mines* 
Quarries and Collieries. Illustrated by 148 engravings of Geological 
Formations, Mining Operations and Machinery, drawn from the 
practice of all parts of the world. 2d Edition, i2mo., 450 pages $5.0(8 

DAVIES. — A Treatise on Slate and Slate Quarrying: 
Scientific, Practical and Commercial. By D. C. Davies, F. G. S., 1 
Mining Engineer, etc. With numerous illustrations and folding 
plates, iamo. . $2.03 

DAVIS. — A Treatise on Steam-Boiler Incrustation and Meth- 
ods for Preventing Corrosion and the Formation of Scale : 

By Charles T. Davis. Illustrated by 65 engravings. 8vo. $1.50 

DAVIS.— The Manufacture of Paper: 

Being a Description of the various Processes for the Fabrication, 
Coloring and Finishing of every kind of Paper, Including the Dif- 
ferent Raw Materials and the Methods for Determining their Values, 
the Tools, Machines and Practical Details connected with an intelli- 
gent and a profitable prosecution of the art, with special reference to 
the best American Practice. To which are added a History of Pa- 
per, complete Lists of Paper-Making Materials, List of American 
Machines, Tools and Processes used in treating the Raw Materials, 
and in Making, Coloring and Finishing Paper. By Charles T. 
Davis. Illustrated by 156 engravings. 608 pages, 8vo. #6.00 

DAVIS.— The Manufacture of Leather: 
Being a description of all of the Processes for the Tanning, Tawing, 
Currying, Finishing and Dyeing of every kind of Leather ; including 
the various Raw Materials and the Methods for Determining their 
Values; the Tools, Machines, and all Details of Importance con- 
nected with an Intelligent and Profitable Prosecution of the Art, with 
Special Reference to the Best American Practice. To which are 
added Complete Lists of all American Patents for Materials, Pro- 
cesses, Tools, and Machines for Tanning, Currying, etc. By Charles 
Thomas Davis. Illustrated by 302 engravings and 12 Samples of 
Dyed Leathers. One vol., 8vo., 824 pages . . . $10.00 

DAWIDOWSKY— BRANNT.— A Practical Treatise on the 

Raw Materials and Fabrication of Glue, Gelatine, Gelatine 

Veneers and Foils, Isinglass, Cements, Pastes, Mucilages, 

etc.: 

Eased upon Actual Experience. By F. Dawidowsky, Technical 

Chemist. Translated from the German, with extensive additions, 

including a description of the most Recent American Processes, by 

William T. Brannt, Graduate of the Royal Agricultural College 

of Eldena, Prussia. 35 Engravings. l2mo. . . . #2.50 

RE GRAFF. — The Geometrical Stair-Builders' Guide : 
Being a Plain Practical System of Hand-Railing, embracing all ita 
necessary Details, and Geometrically Illustrated by twenty-two Stee! 
Engravings ; together with the use of the most approved principles 
of Practical Geometry. By Simon De Graff, Architect. |to. 

#2.50 






HENRY CAREY BaiKi3 & CO .3 CATALOGUE. n 



DF KONINCK— DIETZ.— A Practical Manual of Chemical 
Analysis and Assaying : 

As applied to the Manufacture of Iron from its Ores, and to Cast Iron, 
Wrought Iron, and Steel, as found in Commerce. By L. L. Dfi 
Koninck, Dr. Sc, and E. Dietz, Engineer. Edited with Notes, by 
Robert Mallet, F. R. S., F. S. G., M. I. C. E., etc. American 
Edition, Edited with Notes and an Appendix on Iron Ores, by A. A. 
Fesquet, Chemist and Engineer. i2mo. . . . $2.50 

DUNCAN.— Practical Surveyor's Guide: 

Containing the necessary information to make any person of com- 
mon capacity, a finished land surveyor without the aid of a teacher 
By Andrew Duncan. Illustrated. i2mo. . . . $1.25 

DUPLAIS. — A Treatise on the Manufacture and Distillation 
of Alcoholic Liquors : 
Comprising Accurate and Complete Details in Regard to Alcohol 
from Wine, Molasses, Beets, Grain, Rice, Potatoes, Sorghum, Aspho- 
del, Fruits, etc.; with the Distillation and Rectification of Brandy. 
Whiskey, Rum, Gin, Swiss Absinthe, etc., the Preparation of Aro- 
matic Waters, Volatile Oils or Essences, Sugars, Syrups, Aromatic 
Tinctures, Liqueurs, Cordial Wines, Effervescing Wines, etc., the 
Ageing of Brandy and the improvement of Spirits, with Copioua 
Directions and Tables for Testing and Reducing Spirituous Liquors, 
etc., etc. Translated and Edited from the French of MM. Duplais, 
Aine et Jeune. By M. McKennie, M. D. To which are added the 
United States Internal Revenue Regulations for the Assessment and 
Collection of Taxes on Distilled Spirits. Illustrated by fourteen 
folding plates and several wood engravings. 743 pp. 8vo. $10 00 

BUSSAUCE,— Practical Treatise on the Fabrication of Matches, 
Gun Cotton, and Fulminating Powder. 
By Professor H. Dussauce. i2mo. . . . . I3 oo 

OYER AND COLOR-MAKER'S COMPANION: 

Containing upwards of two hundred Receipts for making Colors, on 
the most approved principles, for all the various styles and fabrics now 
in existence; with the Scouring Process, and plain Directions for 
Preparing, Washing-off, and Finishing the Goods. i2mo. |i 25 

EDWARDS.— A Catechism of the Marine Steam-Engine, 

For the use of Engineers, Firemen, and Mechanics. A Practical 
Work for Practical Men. By Emory Edwards, Mechanical Engi- 
neer. Illustrated by sixty-three Engravings, including examples of 
the most modern Engines. Third edition, thoroughly revised, with 
much additional matter. 1 2 mo. 414 pages . . . $2 00 

tDWARDS. — Modern American Locomotive Engines, 

Their Design, Construction and Management. By Emory Edwards, 
Illustrated i2mo #2.00 

EDWARDS.— The American Steam Engineer: 

Theoretical and Practical, with examples of the latest and most ap- 
proved American practice in the design and construction of Steam 
Engines and Boilers. For the use of engineers, machinists, boiler- 
pikers, and engineering students. By Emory Edwards. Fully 
'-illustrated, 419 pages. i2mo. .... $2.50 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 



EDWARDS. — Modern American Marine Engines, Boilers, an$ 
Screw Propellers, 

Their Design and Construction. Showing the Present Practice of 
the most Eminent Engineers and Marine Engine Builders in the 
United States. Illustrated by 30 large and elaborate plates. 4to. #5.oq 
EDWARDS.— The Practical Steam Engineer's Guide 
In the Design, Construction, and Management of American Stationary, 
Portable, and Steam Fire-Engines, Steam Pumps, Boilers, "Injectors, 
Governors, Indicators, Pistons and Rings, Safety Valves and Steam 
Gauges. For the use of Engineers, Firemen, and Steam Users. By 
Emory Edwards. Illustrated by 119 engravings. 420 pages. 
i2mo. .......... $2 50 

EISSLER.— The Metallurgy of Gold : 

A Practical Treatise on the Metallurgical Treatment of Gold-Bear- 
ing Ores, including the Processes of Concentration and Chlorination, 
and the Assaying, Melting, and Refining of Gold. By M. Eissler. 

With 132 Illustrations. i2mo #3-50 

EISSLER.— The Metallurgy of Silver : 

A Practical Treatise on the Amalgamation, Roasting, and Lixiviation 
of Silver Ores, including the Assaying, Melting, and Refining of 
Silver Bullion. By M. Eissler. 124 Illustrations. 336 pp. 

i2mo #4-25 

ELDER. — Conversations on the Principal Subjects of Political 
Economy. 
By Dr. William Elder. 8vo. . . . . . $250 

ELDER.— Questions of the Day, 

Economic and Social. By Dr. William Elder. 8vo. . #3.00 

6RNL— Mineralogy Simplified. 

Easy Methods of Determining and Classifying Minerals, including 
Ores, by means of the Blowpipe, and by Humid Chemical Analysis, 
based on Professor von KobelPs Tables for the Determination of 
Minerals, with an Introduction to Modern Chemistry. By Henry 
Erni, A.M., M.D., Professor of Chemistry. Second Edition, rewritten, 
enlarged and improved. i2mo. . . . . <■ $3 oc 

FAIRBAIRN.— The Principles of Mechanism and Machinery 
of Transmission ■ 
Comprising the Principles of Mechanism, Wheels, and Pullevs, 
Strength and Proportions of Shafts, Coupling of Shafts, and Engag- 
ing and Disengaging Gear. By Sir William Fairbairn, Bait. 
C. E. Beautifully illustrated by over 150 wood-cuts. In one 
volume. i2mo # 2 -5 G 

FLEMING.— Narrow Gauge Railways in America. 
A Sketch of their Rise, Progress, and Success. Valuable Statistics 
as to Grades, Curves, Weight of Rad, Locomotives, Cars, efc. By 
Howard Fleming. Illustrated, 8vo $1 00 

FORSYTH.— Book of Designs for Headstones, Mural, and 
other Monuments : 
Containing 78 Designs. By James Forsyth. With an Introduction 
hy Charles Boutell, M. A. 4 to., cloth . . - #5 °° 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 13 



FRANKEL— HUTTER. — A Practical Treatise on the Manu* 
facture of Starch, Glucose, Starch-Sugar, and Dextrine: 
Based on the German of Ladislaus Von Wagner, Professor in the 
Royal Technical High School, Buda-Pest, Hungary, and other 
authorities. By Julius Frankel, Graduate of the Polytechnic 
School of Hanover. Edited by Robert Hutter, Chemist, Practical 
Manufacturer of Starch-Sugar. Illustrated by 58 engravings, cover- 
ing every branch of the subject, including examples of the most 
Recent and Best American Machinery. 8vo., 344 pp. . $3S° 

GARDNER.— The Painter's Encyclopaedia: 

Containing Definitions of all Important Words in the Art of Plain 
and Artistic Painting, with Details of Practice in Coach, Carriage, 
Railway Car, House, Sign, and Ornamental Painting, including 
Graining, Marbling, Staining, Varnishing, Polishing, Lettering, 
Stenciling, Gilding, Bronzing, etc. By Franklin B. Gardner. 
158 Illustrations. 121110. 427 pp #2.oc 

GARDNER.— Everybody's Paint Book: 

A Complete Guide to the Art of Outdoor and Indoor Painting, De- 
signed for the Special Use of those who wish to do their own work, 
and consisting of Practical Lessons in Plain Painting, Varnishing, 
Polishing, Staining, Paper Hanging, Kalsomining, etc., as well as 
Directions for Renovating Furniture, and Hints on Artistic Work for 
Home Decoration. 38 Illustrations. i2mo., 183 pp. . $1.00 

GEE.— The Goldsmith's Handbook : 

Containing full instructions for the Alloying and Working of Gold, 
including the Art of Alloying, Melting, Reducing, Coloring, Col- 
lecting, and Refining; the Processes of Manipulation, Recovery of 
Waste; Chemical and Physical Properties of Gold; with a New 
System of Mixing its Alloys; Solders, Enamels, and other Useful 
Rules and Recipes. By George E. Gee. i2mo. . . #1-75 

GEE.— The Silversmith's Handbook : 

Containing full instructions for the Alloying and Working of Silver, 
including the different modes of Refining and Melting the Metal ; its 
Solders ; the Preparation of Imitation Alloys ; Methods of Manipula- 
tion ; Prevention of Waste ; Instructions for Improving and Finishing 
the Surface of the Work ; together with other Useful Information and 
Memoranda. By George E. Gee. Illustrated. i2mo. #1.75 

GOTHIC ALBUM FOR CABINET-MAKERS: 

Designs for Gothic Furniture. Twenty-three plates. Oblong $2.00 

GRANT.— A Handbook on the Teeth of Gears : 

Their Curves, Properties, and Practical Construction. By George 
B. Grant. Illustrated. Third Edition, enlarged. 8vo. #1.50 

GREENWOOD.— Steel and Iron: 

Comprising the Practice and Theory of the Several Methods Pur* 
sued in their Manufacture, and of their Treatment in the Rolling- 
Mills, the Forge, and the Foundry. By William Henry Green- 
wood, F. C. S. With 97 Diagrams, 536 pages. i2mo. £2.00 



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GREGORY.— Mathematics for Practical Men : 

Adapted to the Pursuits of Surveyors, Architects, Mechanics, and 
Civil Engineers. By OlinthUS Gregory. 8vo., plates #3.00 

GRIMSHAW.— Saws : 

The History, Development, Action, Classification, and Comparison 
of Saws of all kinds. With Copious Appendices. Giving the details 
of Manufacture, Filing, Setting, Gumming, etc. Care and Use of 
Saws; Tables of Gauges; Capacities of Saw-Mills; List of Saw- 
Patents, and other valuable information. By ROBERT GriMSHAW. 
Second and greatly enlarged edition, with Supplement^ and 354 
Illustrations. Quarto #5.00 

GRISWOLD. — Railroad Engineer's Pocket Companion for the 
Field : 
Comprising Rules for Calculating Deflection Distances and Angles, 
Tangential Distances and Angles, and all Necessary Tables for En> 
gineers; also the Art of Levelling from Preliminary Survey to tha 
Construction of Railroads, intended Expressly for the Young En- 
gineer, together with Numerous Valuable Rules and Examples. By 
W. Griswold. i2mo., tucks $ T -75 

GRUNER. — Studies of Blast Furnace Phenomena: 

By M. L. Gruner, President of the General Council of Mines of 
France, and lately Professor of Metallurgy at the Ecole des Mines. 
Translated, with the author's sanction, with an Appendix, by L. D. 
B. Gordon, F. R. S. E., F. G. S. 8vo. . . . #2.50 

Hand-Book of Useful Tables for the Lumberman, Farmer and 
Mechanic: 
Containing Accurate Tables of Logs Reduced to Inch Board Meas* 
ure, Plank, Scantling and Timber Measure ; Wages and Rent, by 
Week or Month ; Capacity of Granaries, Bins and Cisterns ; Land 
Measure, Interest Tables, with Directions for Finding the Interest on 
any sum at 4, 5, 6, 7 and 8 per Cent., and many other Useful Tables. 
32 mo., boards. 186 pages .25 

HASERICK.— The Secrets of the Art of Dyeing Wool, Cotton, 
and Linen, 
Including Bleaching and Coloring Wool and Cotton Hosiery and 
Random Yarns. A Treatise based on Economy and Practice. By 
E. C. Haserick. Illustrated by 323 Dyed Patterns of the Yami 
or Fabrics. 8vo #7-50 

HATS AND FELTING : 

A Practical Treatise on their Manufacture. By a Practical Flatter. 
Illustrated by Drawings of Machinery, etc. 8vo. . . #r.2$ 

HOFFER. — A Practical Treatise on Caoutchouc and Gutta 

Percha, 

Comprising the Properties of the Raw Materials, and the manner of" 

Mixing and Working them ; with the Fabrication of Vulcanized and 

Hard Rubbers, Caoutchouc and Gutta Per-cha Compositions, Water. 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 15 

proof Substances, Elastic Tissues, the Utilization of Waste, etc., etc. 
From the German of Raimund Hoffer. By W. T. Erannt. 
Illustrated i2mo $2.50 

HOFMANN.— A Practical Treatise on the Manufacture of 
Paper in all its Branches : 
By Carl Hofmann, Late Superintendent of Paper-Mills in German} 
and the United States ; recently Manager of the " Public Ledger " 
Paper-Mills, near Elkton, Maryland. Illustrated by no wood en- 
gravings, and five large Folding Plates. 4to., cloth; about 400 
pages .... $35.00 

HUGHES. — American Miller and Millwright's Assistant: 
By William Carter Hughes. i2mo $1.50 

HULME. — Worked Examination Questions in Plane Geomet- 
rical Drawing : 
For the Use of Candidates for the Royal Military Academy, Wool- 
wich; the Royal Military College, Sandhurst; the Indian Civil En* 
gineering College, Cooper's Hill ; Indian Public Works and Tele- 
graph Departments ; Royal Marine Light Infantry ; the Oxford and 
Cambridge Local Examinations, etc. By F. Edward Hulme, F. L. 
S., F. S. A., Art-Master Marlborough College. Illustrated by 300 
examples. Small quarto . . . . . S2.50 

JERVIS.— Railroad Property: 

A Treatise on the Construction and Management of Railways; 
designed to afford useful knowledge, in the popular style, to the 
holders of this class of property ; as well as Railway Managers, Offi. 
cers, and Agents. By JoHN B. JeRVIS, late Civil Engineer of the 
Hudson River Railroad, Croton Aqueduct, etc. i2mo., cloth $2.oc 

KEENE.— A Hand-Book of Practical Gauging: 

For the Use of Beginners, to which is addad a Chapter on Distilla* 
tion, describing the process in operation at the Custom-House for 
ascertaining the Strength of Wines. By James B. Keene, of H. M. 
Customs. 8vo. ........ $125 

KELLEY.— Speeches, Addresses, and Letters on Industrial and 
Financial Questions : 
By Hon. William D. Kelley, M. C. 544 pages, 8vo. . #3.00 

KELLOGG. — A New Monetary System : 

The only means of Securing the respective Rights of Labor and 
Property, and of Protecting the Public from Financial Revulsions. 
By Edward Kellogg. Revised from his work on " Labor and 
other Capital." With numerous additions from his manuscript. 
Edited by Mary Kellogg Putnam. Fifth edition. To which is 
added a Biographical Sketch of the Author. One volume, i2mo. 

Paper cover $1.00 

Bound in cloth 1-5° 

KEMLO.— Watch-Repairer's Hand-Book: 
Being a Complete Guide to the Young Beginner, in Taking Apart, 
Putting Together, and Thoroughly Cleaning the English Lever and 
other Foreign Watches, and all American Watches. By F. Kemlo, 
Practical Watchmaker. With Illustrations. 12m©. . #l.2f 



16 HENRY CAREY BAIRD & CO.'S CATALOGUE. 

KENTISH.— A Treatise on a Box of Instruments, 

And the Slide Rule ; with the Theory of Trigonometry and Log* 
rithms, including Practical Geometry, Surveying, Measuring of Tim. 
ber, Cask and Malt Gauging, Heights, and Distances. By ThomaJ 
Kentish. In one volume. i2mo. . . . #i.2§ 

KERL.— The Assayer's Manual: 

An Abridged Treatise on the Docimastic Examination of Ores, and 
Furnace and other Artificial Products. By Bruno Kerl, Professor 
in the Royal School of Mines. Translated from the German by 
William T. Brannt. Second American edition, edited with Ex- 
tensive Additions by F. Lynwood Garrison, Member of the 
American Institute of Mining Engineers, etc. Illustrated by 87 en- 
gravings. 8vo . . #3.00 

KJCK.— Flour Manufacture. 

A Treatise on Milling Science and Practice. By Frederick Kick, 
Imperial Regierungsrath, Professor of Mechanical Technology in the 
imperial German Polytechnic Institute, Prague. Translated from 
the second enlarged and revised edition with supplement by H. H. 
P. Powles, Assoc. Memb. Institution of Civil Engineers. Illustrated 
with 28 Plates, and 167 Wood-cuts. 367 pages. 8vo. . #10.00 

KINGZETT.— The History, Products, and Processes of the 
Alkali Trade : 
Including the most Recent Improvements. By Charles Thomas 
Kingzett, Consulting Chemist. With 23 illustrations. 8vo. #2.50 

K IRK.— The Founding of Metals : 

A Practical Treatise on the Melting of Iron, with a Description of the 
Founding of Alloys; also, of all the Metals and Mineral Substances 
used in the Art of Founding. Collected from original sources. B> 
Edward Kirk, Practical Foundryman and Chemist. Illustrated. 
Third edition. 8vo #2.50 

LANDRIN.— A Treatise on Steel : 
Comprising its Theory, Metallurgy, Properties, Practical Working, 
and Use. By M. H. C. Landrin, Jr., Civil Engineer. Translated 
from the French, with Notes, by A. A. Fesquet, Chemist and En- 
gineer. With an Appendix on the Bessemer and the Martin Pro- 
poses for Manufacturing Steel, from the Report of Abram S. Hewitt- 
United States Commissioner to the Universal Exposition, Paris, 1867. 
l2mo #3-°° 

LANGBEIN.— A Complete Treatise on the Electro-Deposition 
of Metals : 
Translated from the German, with Additions, by Wm. T. Brannt. 
125 illustrations. 8vo #4-00 

LARDNER.— The Steam-Engine : 

For the Use of Beginners. Illustrated. l2mo. . • • 75 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 17 

LARKIN. — The Practical Brass and Iron Founder's Guide; 
A Concise Treatise on Brass Founding, Moulding, the Metals and 
their Alloys, etc.; to which are added Recent Improvements in the 
Manufacture of Iron, Steel by the Bessemer Process, etc., etc. By 
James Larkin, late Conductor of the Brass Foundry Department iu 
Reany, Neafie & Co.'s Penn Works, Philadelphia. Fifth edition, 
revised, with extensive additions. l2mo. . . . $2.25 

I^ROUX.— A Practical Treatise on the Manufacture of 
Worsteds and Carded Yarns : 
Comprising Practical Mechanics, with Rules and Calculations applied 
to Spinning; Sorting, Cleaning, and Scouring Wools; the English 
and French Methods of Combing, Drawing, and Spinning Worsteds, 
and Manufacturing Carded Yarns. Translated from the French of 
Charles Leroux, Mechanical Engineer and Superintendent of a 
Spinning-Mill, by Horatio Paine, M. D., and A. A. Fesquet, 
Chemist and Engineer. Illustrated by twelve large Plates. To which 
is added an Appendix, containing Extracts from the Reports of the 
International Jury, and of the Artisans selected by the Committee 
appointed by the Council of the Society of Arts, London, on Woolen 
and Worsted Machinery and Fabrics, as exhibited in the Paris Uni- 
versal Exposition, 1867. 8vo. $5-00 

LEFFEL. — The Construction of Mill-Dams : 
Comprising also the Building of Race and Reservoir Embankments 
and Head-Gates, the Measurement of Streams, Gauging of Water 
Supply, etc. By James Leffel & Co. Illustrated by 58 engravings. 
8vo. . #2.50 

LESLIE.— Complete Cookery: 
Directions for Cookery in its Various Branches. By Miss Leslie. 
Sixtieth thousand. Thoroughly revised, with the addition of New 
Receipts. i2mo $1.50 

LE VAN. — The Steam Engine and the Indicator : 

Their Origin and Progressive Development ; including the Most 
Recent Examples of Steam and Gas Motors, together with the Indi- 
cator, its Principles, its Utility, and its Application. By William 
Barnet Le Van. Illustrated by 205 Engravings, chiefly of Indi- 
cator-Cards. 469 pp. 8vo £4.00 

ClEBER. — Assayer's Guide : 
Or, Practical Directions to Assayers, Miners, and Smelters, for the 
Tests and Assays, by Heat and by Wet Processes, for the Ores of all 
the principal Metals, of Gold and Silver Coins and Alloys, and of 
Coal, etc. By Oscar M. Lieber. i2mo. . . . $1.25 

Lockwood's Dictionary of Terms : 
Used in the Practice of Mechanical Engineering, embracing those 
Current in the Drawing Office, Pattern Shop, Foundry, Fitting, Turn- 
ing, Smith's and Boiler Shops, etc., etc., comprising upwards of Six 
Thousand Definitions. Edited by a Foreman Pattern Maker, author 
of " Pattern Making." 417 pp. i2mo. . . . $3 -oo 



i8 HENRY CAREY BAIRD & CO.'S CATALOGUE. 

LUKIN. — Amongst Machines; 

Embracing Descriptions of the various Mechanical Appliances used 
in the Manufacture of Wood, Metal, and other Substances. J2mo. 

MJKIN.— The Boy Engineers: 
What They Did, and How They Did It. With 30 plates. i8mo. 

LUKIN.— The Young Mechanic : 

Practical Carpentry. Containing Directions for the Use of all kinds 
:of Tools, and for Construction of Steam- Engines and Mechanical 
Models, including the Art of Turning in Wood and Metal. By John 
Lukin, Author of "The Lathe and Its Uses," etc. Illustrated. 
l2mo $ 1 .75 

MAIN and BROWN. — Questions on Subjects Connected with 

the Marine Steam-Engine : 

And Examination Papers; with Hints for their Solution. By 

Thomas J. Main, Professor of Mathematics, Royal ""tfaval College, 

and Thomas Brown, Chief Engineer, R. N. i2mo., cloth . $1.50 

MAIN and BROWN. — The Indicator and Dynamometer: 
With their Practical Applications to the Steam-Engine. By Thomas 
J. Main, M. A. F. R., Ass't S. Professor Royal Naval College, 
Portsmouth, and Thomas Brown, Assoc. Inst. C. E., Chief Engineer 
R. N., attached to the R. N. College. Illustrated. 8vo. . #1.50 

MAIN and BROWN.— The Marine Steam-Engine. 

By Thomas J. Main, F. R. Ass't S. Mathematical Professor at the 
Royal Naval College, Portsmouth, and THOMAS Brown, Assoc. 
Inst. C. E., Chief Engineer R. N. Attached to the Royal Naval 
College. With numerous illustrations. 8vo. . . $5.00 

MAKINS.— A Manual of Metallurgy: 

By George Hogarth Makins. 100 engravings. Second edition 
rewritten and much enlarged. i2mo., 592 pages . . $3-oo 

MARTIN.— Screw-Cutting Tables, for the Use of Mechanical 
Engineers : 
Showing the Proper Arrangement of Wheels for Cutting the Threads 
of Screws of any Required Pitch ; with a Table for Making the Uni- 
versal Gas-Pipe Thread and Taps. By W. A. Martin, Engineer. 
8vo. 50 

MICHELL.— Mine Drainage: 
Being a Complete and Practical Treatise on Direct-Acting Under- 
ground Steam Pumping Machinery. With a Description of a larg« 
number of the best known Engines, their General Utility and th« 
Special Sphere of their Action, the Mode of their Application, and 
their Merits compared with other Pumping Machinery. By Stephen 
Michell. Illustrated by 137 engravings. 8vo., 277 pages . $6.00 

feOLESWORTH.— Pocket-Book of Useful Formulae and 
Memoranda for Civil and Mechanical Engineers. 
By Guilford L. Molesworth, Member of the Institution of Civi? 
Engineers, Chief Resident Engineer of the Ceylon Railway. Full- 
bound in Pocket-book form • $1,0* 



HENRY CAREY BAIRD & CO.fr CATALOGUE. 19 

MOORE. — The Universal Assistant and the Complete Me- 
chanic : 

Containing over one million Industrial Facts, Calculations, Receipts, 
Processes, Trades Secrets, Rules, Business Forms, Legal Items, Etc., 
in every occupation, from the Household to the Manufactory. By 
R.Moore. Illustrated by 500 Engravings. i2mo. . $2.50 

MORRIS. — Easy Rules for the Measurement of Earthworks : 
By means of the Prismoidal Formula. Illustrated with Numerous 
Wood-Cuts, Problems, and Examples, and concluded by an Exten- 
sive Table for finding the Solidity in cubic yards from Mean Areas. 
The whole being adapted for convenient use by Engineers, Surveyors, 
Contractors, and others needing Correct Measurements of Earthwork. 
By Elwood Morris, C. E. 8vo #1.50 

fcSORTON. — The System of Calculating Diameter, Circumfer- 
ence, Area, and Squaring the Circle : 
Together with Interest and Miscellaneous Tables, and other informa- 
tion. By James Morton. Second Edition, enlarged, with the 
Metric System. i2mo. ....... $i.otl 

NAPIER.— Manual of Electro -Metallurgy: 

Including the Application of the Art to Manufacturing Processes. 
By James Napier. Fourth American, from the Fourth London 
edition, revised and enlarged. Illustrated by engravings. 8vo. 

NAPIER. — A System of Chemistry Applied to Dyeing. 

By James Napier, F. C. S. A New and Thoroughly Revised Edi- 
tion. Completely brought up to the present state of the Science, 
including the Chemistry of Coal Tar Colors, by A. A. Fesquet, 
Chemist and Engineer. With an Appendix on Dyeing and Calico 
Printing, as shown at the Universal Exposition, Paris, 1867. Illus- 
trated. 8vo. 422 pages $3-5° 

NEVILLE.— Hydraulic Tables, Coefficients, and Formulae, for 
finding the Discharge of Water from Orifices, Notches, 
Weirs, Pipes, and Rivers : 
Third Edition, with Additions, consisting of New Formulae for the 
Discharge from Tidal and Flood Sluices and Siphons ; general infor- 
mation on Rainfall, Catchment-Basins, Drainage, Sewerage, Water 
Supply for Towns and Mill Power. By Tohn Neville, C. E. M. R. 
I. A. ; Fellow of the Royal Geological Society of Ireland. Thick 
l2mo $5.50 

NEWBERY.- Gleanings from Ornamental Art of every 
style : 
Drawn from Examples in the British, South Kensington, Indian, 
Crystal Palace, and other Museums, the Exhibitions of 1851 and 
1862, and the best English and Foreign works. In a series of 100 
exquisitely drawn Plates, containing many hundred examples. B* 
Robert Newbery. 4to. $12.50 

UICHOLLS.— The Theoretical and Practical Boiler-Maker and 
Engineer's Reference Book: 
Containing a variety of Useful Information for Employers of Labor. 
Foremen and Working Boiler- Makers, Iroxx, Copper, and Tinsmith* 



20 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 



Draughtsmen, Engineers, the General Steam-using Public, and for tha 
Use of Science Schools and Classes. By Samuel Nicholls. Illus. 
trated by sixteen plates, i2mo. $2.50 

NICHOLSON.— A Manual of the Art of Bookbinding : 

Containing full instructions in the different Branches of Forwarding, 
Gilding, and Finishing. Also, the Art of Marbling Book-edges and 
Paper. By James B. Nicholson. Illustrated. i2mo., cloth #2.25 

NICOLLS.— The Railway Builder: 

A Hand-Book for Estimating the Probable Cost of American Rail- 
way Construction and Equipment. By William J. Nicolls, Civil 
Engineer. Illustrated, full bound, pocket-book form . $2.00" 

NORMANDY.— The Commercial Handbook of Chemical An- 
alysis : 
Or Practical Instructions for the Determination of the Intrinsic 01 
Commercial Value of Substances used in Manufactures, in Trades, 
and in the Arts. By A. Normandy. New Edition, Enlarged, and 
to a great extent rewritten. By Henry M. Noad, Ph.D., F.R.S., 
thick i2mo . $5.00 

MORRIS. — A Handbook fcr Locomotive Engineers and Ma- 
chinists : 
Comprising the Proportions and Calculations for Constructing Loco- 
motives; Manner of Setting Valves; Tables of Squares, Cubes, Areas, 
etc., etc. By Sefhmus Norris, M. E. New edition. Illustrated, 
l2mo $1.50 

NYSTROM. — A New Treatise on Elements of Mechanics : 
Establishing Strict Precision in the Meaning of Dynamical Terms : 
accompanied with an Appendix on Duodenal Arithmetic and Me- 
trology. By John W. Nystrom, C. E. Illustrated. 8vo. $2.00 

NYSTROM. — On Technological Education and the Construc- 
tion of Ships and Screw Propellers : 
For Naval and Marine Engineers. By John W. Nystrom, late 
Acting Chief Engineer, U. S. N. Second edition, revised, with addi- 
tional matter. Illustrated by seven engravings. i2mo. . $1.50 

"3'NEILL. — A Dictionary of Dyeing and Calico Printing: 
Containing a brief account of all the Substances and Processes in 
use in the Art of Dyeing and Printing Textile Fabrics ; with Practical 
Receipts and Scientific Information. By Charles O'Neill, Analy- 
tical Chemist. To which is added an Essay on Coal Tar Colors and 
their application to Dyeing and Calico Printing. By A. A. Fesquet, 
Chemist and Engineer. With an appendix on Dyeing and Calico 
Printing, as shown at the Universal Exposition, Paris, 1867. 8vo., 
491 pages #3.50 

&RTON. — Underground Treasures*. 

How and Where to Find Them. A Key for the Ready Determination 
of ail the Useful Minerals within the United States. By James 
Orton, A.M., Late Professor of Natural History in Vassar College, 
N. Y.; Cor. Mem. of the Academy of Natural Sciences, Philadelphia, 
and of the Lyceum of Natural History, New York ; author of the 
"Andes and the Amazon," etc. A New Edition, with Additions. 
Illustrated «. #1.50 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 



OSBORN — The Metallurgy of Iron and Steel: 

Theoretical and Practical in all its Branches ; with special reff rencc 
to American Materials and Processes. By H. S. O.^born, LL. D,, 
Professor of Mining and Metallurgy in Lafayette College, Easton, 
Pennsylvania. Illustrated by numerous large folding plates and 
wood-engravings. 8vo. ...... $25.00 

OSBORN. — A Practical Manual of Minerals, Mines and Mhv 

» ing: 

Comprising the Physical Properties, Geologic Positions, Local Occur- 
rence and Associations of the Useful Minerals; their Methods of 
Chemical Analysis and Assay : together with Various Systems of 
Excavating and Timbering, Brick and Masonry Work, during Driv- 
ing, Lining, Bracing and other Operations, etc. By Prof. H. S. 
Osborn, LL. D., Author of the " Metallurgy of Iron and Steel." 
Illustrated by 17 1 engravings from original drawings. 8vo. $4-5° 

OVERMAN.— The Manufacture of Steel : 

Containing the Practice and Principles of Working and Making Steel. 
A Handbook for Blacksmiths and Workers in Steel and Iron, Wagon 
Makers, Die Sinkers, Cutlers, and Manufacturers of Files and Hard- 
ware, of Steel and Iron, and for Men of Science and Art. By 
Frederick Overman, Mining Engineer, Author of the " Manu- 
facture of I*on," etc. A new, enlarged, and revised Edition. By 
A. A. Fesqtjst, Chemist and Engineer. l2mo. . . $1.56 

OVERMAN.— The Moulder's and Founder's Pocket Guide : 
A Treatise or* Moulding and Founding in Green-sand, Dry-sand, Loam, 
and Cement; the Moulding of Machine Frames, Mill-gear, Hollow- 
ware, Ornaments, Trinkets, Bells, and Statues ; Description of Moulds 
for Iron, Bronze, Brass, and other Metals ; Plaster of Paris, Sulphur, 
Wax, etc. ; the Construction of Melting Furnaces, the Melting and 
Founding of Metals ; the Composition of Alloys and their Nature, 
etc., etc. By Frederick Overman, M. E. A new Edition, to 
which is added a Supplement on Statuary and Ornamental Moulding, 
Ordnance, Malleable Iron Castings, etc. By A. A. Fesquet, Chem- 
ist and Engineer. Illustrated by 44 engravings. i2mo. . $2.00 

PAINTER, GILDER, AND VARNISHER'S COMPANION; 
Containing Rules and Regulations in everything relating to the ArtS 
of Painting, Gilding, Varnishing, Glass-Staining, Graining, Marbling, 
Sign-Writing, Gilding on Glass, and Coach Painting and Varnishing; 
Tests for the Detection of Adulterations in Oils, Colors, etc. ; and a 
Statement of the Diseases to which Painters are peculiarly liable, with 
the Simplest and Best Remedies. Sixteenth Edition. Revised, with 
an Appendix. Containing Colors and Coloring — Theoretical and 
Practical. Comprising descriptions of a great variety of Additional 
Pigments, their Qualities and Uses, to which are added, Dryers, and 
Modes and Operations of Painting, etc. Together with Chevreui's 
Principles of Harmony and Contrast of Colors. i2mo. Cloth $1.50 

PALLETT.— The Miller's, Millwright's, and Engineer's Guide. 
By Henry Pallett. Illustrated. i2mo. . . , #2.o» 



22 KENRY CAREY BAIRD & CO.'S CATALOGUE. 

PERCY. — The Manufacture of Russian Sheet-Iron. 

By John Percy, M. D., F. R. S., Lecturer on Metallurgy at th« 
Royal School of Mines, and to The Advance Class of Artillery 
Officers at the Royal Artillery Institution, Woolwich ; Author of 
" Metallurgy." With Illustrations. 8vo., paper . . 50 cts, 

PERKINS.— Gas and Ventilation : 
Practical Treatise on Gas and Ventilation. With Special Relation 
to Illuminating, Heating, and Cooking by Gas. Including Scientific 
Helps to Engineer-students and others. With Illustrated Diagrams, 
By E. E. Perkins, i2mo., cloth $1.25 

PERKINS AND STOWE.-A New Guide to the Sheet-iron 
and Boiler Plate Roller : 
Containing a Series of Tables showing the Weight of Slabs and Piles 
to Produce Boiler Plates, and of the Weight of Piles and the Sizes of 
Bars to produce Sheet-iron ; the Thickness of the Bar Gauge 
in decimals; the Weight per foot, and the Thickness on the Bar or 
Wire Gauge of the fractional parts of an inch; the Weight per 
sheet, and the Thickness on the Wire Gauge of Sheet-iron of various 
dimensions to weigh 112 lbs. per bundle; and the conversion of 
Short Weight into Long Weight, and Long Weight into Short. 
Estimated and collected by G. H. Perkins and J. G. Stowe. $2. 5<s 

POWELL— CHANCE— HARRIS —The Principles of Glass 

Making. 

By Harry J. Powell, B. A. Together with Treatises on Crown and 

Sheet Glass; by Henry Chance, M. A. And Plate Glass, by H. 

G. Harris, Asso. M. Inst. C. E. Illustrated i8mo. . #1.50 

PROCTOR.— A Pocket-Book of Useful Tables and Formulae 
for Marine Engineers : 
By Frank Proctor. Second Edition, Revised and Enlarged. 
Full -bound pocket-book form ...... $1.50 

REGNAULT.— Elements of Chemistry: 

By M. V. Regnault. Translated from the French by T. Forrest 
Betton, M. D., and edited, with Notes, by James C. Booth, Melter 
and Refiner U. S. Mint, and William L. Faber, Metallurgist and 
Mining Engineer. Illustrated by nearly 700 wood-engravings. Com- 
prising nearly 1,500 pages. In two volumes, 8vo., cloth . $7.50 

RICHARDS.— Aluminium : 

Its History, Occurrence, Properties, Metallurgy and Applications, 
including its Alloys. By Joseph W. Richards, A. C, Chemist and 
Practical Metallurgist, Member of the Deutsche Chemische Gesell- 
schaft. Illustrated #5-00 

RIFFAULT, VERGNAUD, and TOUSSAINT.— A Practical 
Treatise on the Manufacture of Colors for Painting : 
Comprising the Origin, Definition, and Classification of Colors; the 
Treatment of the Raw Materials; the best Formulae and the Newest 
Processes for the Preparation of every description of Pigment, and 
the Necessary Apparatus and Directions for its Use; Dryers; the 
Testing, Application, and Qualities of Paints, etc., etc. By MM. 
Riffault, Vergnaud> and Toussaint. Revised and Edited by M. 



HENRY CAREY BAIRD & CO.'S CATALOGUE. i% 

V. Malepeyre. Translated from the French, by A. A. FesqUET}. 
Chemist and Engineer. Illustrated by Eighty engravings. In one 
vol.. 8vo., 659 pages . $75^ 

ROPER. — A Catechism of High-Pressure, or Non-Condensing 
Steam-Engines : 
Including the Modelling, Constructing, and Management of Steam- 
Engines and Steam Boilers. With valuable illustrations. By Ste- 
phen Roper, Engineer. Sixteenth edition, revised and enlarged. 
l8mo., tucks, gilt edge . $2.00 

£OPER.— Engineer's Handy-Book: 

Containing a full Explanation of the Steam-Engine Indicator, and its 
Use and Advantages to Engineers and Steam Users. With Formula& 
for Estimating the Power of all Classes of Steam-Engines; also. 
Facts, Figures, Questions, and Tables for Engineers who wish to 
qualify themselves for the United States Navy, the Revenue Service, 
the Mercantile Marine, or to take charge of the Better Class of Sta- 
tionary Steam-Engines. Sixth edition. l6mo.. 690 pag^s, tucks, 
gilt edge . #3.50 

ROPER. — Hand-Book of Land and Marine Engines : 

Including the Modelling, Construction, Running, and Management 
of Lane 1 and Marine Engines and Boilers. With illustrations. By 
Stephen Roper, Engineer. Sixth edition. i2mo., ticks, gilt edge. 

$3-50 
ROPER.— Hand-Book of the Locomotive : 

Including the Construction of Engines and Boilers, and the Construc- 
tion, Management, and Running of Locomotives. By Stephen 
Roper. Eleventh edition. i8mo., tucks, gilt edge . #2.50 

ROPER. — Hand-Book of Modern Steam Fire-Engines. 

With illustrations. By Stephen Roper, Engineer. Fourth edition, 
i2mo., tucks, gilt edge $3-50 

ROPER. — Questions and Answers for Engineers. 

This little book contains all the Questions that Engineers will be 
asked when undergoing an Examination for the purpose of procuring 
Licenses, and they are so plain that any Engineer or Fireman of or- 
dinary intelligence may commit them to memory in a short time. By 
Stephen Roper, Engineer. Third edition . . . $3.00 

ROPER.— Use and Abuse of the Steam Boiler. 
By Stephen Roper, Engineer. Eighth edition, with illustrations. 
l8mo., tucks, gilt edge ....... $2.00 

ROSE. — The Complete Practical Machinist: 

Embracing Lathe Work, Vise Work, Drills and Drilling, Taps and 
Dies, Hardening and Tempering, the Making and Use of Tools, 
Tool Grinding, Marking out W 7 ork, etc. By Joshua Rose. Illus- 
trated by 356 engravings. Thirteenth edition, thoroughly revised* 
and in great part rewritten. In one vol., i2mo., 439 pages #2.50 

&OSE. — Mechanical Drawing Self-Taught: 
Comprising Instructions in the Selection and Preparation of Drawing 
Instruments, Elementary Instruction in Practical Mechanical Draw- 



24 HENRY CAREY BAIRD & CO.'S CATALOGUE. 

ing, together with Examples in Simple Geometry and Elementary 
Mechanism, including Screw Threads, Gear Wheels, Mechanical 
Motions, Engines and Boilers. By Joshua Rose, M. E. Illustrated 
by 330 engravings. 8vo ,313 pages .... #4.00 

ROSE.— The Slide- Valve Practically Explained: 

Embracing simple and complete Practical Demonstrations of th. 
operation of each element in a Slide-valve Movement, and illustrat- 
ing the effects of Variations in their Proportions by examples care- 
fully selected from the most recent and successful practice. By 
Joshua Rose, M. E. Illustrated by 35 engravings . $1.00 

ROSS. — The Blowpipe in Chemistry, Mineralogy and Geology: 
Containing all Known Methods of Anhydrous Analysis, many Work- 
ing Examples, and Instructions for Making Apparatus. By Lieut. - 
Colonel W. A. Ross, R. A., F. G. S. With 120 Illustrations. 
i2mo #2.00 

SHAW.— Civil Architecture : 

Being a Complete Theoretical and Practical System of Building, con- 
taining the Fundamental Principles of the Art. By Edward Shaw, 
Architect. To which is added a Treatise on Gothic Architecture, etc. 
By Thomas W. Silloway and George M. Harding, Architects. 
The whole illustrated by 102 quarto plates finely engraved on copper. 
Eleventh edition. 4to. ....... $10.00 

SHUNK. — A Practical Treatise on Railway Curves and Loca- 
tion, for Young Engineers. 
By W. F. Shunk, C. E. l2mo. Full bound pocket-book form $2.00 
SLATER.— The Manual of Colors and Dye Wares. 

By J. W. Slater. i2mo #3-75 

SLOAN. — American Houses : 

A variety of Original Designs for Rural Buildings. Illustrated by 
26 colored engravings, with descriptive references. By Samuel 
Sloan, Architect. 8vo. $150 

SLOAN. — Homestead Architecture : 

Containing Forty Designs for Villas, Cottages, and Farm-houses, with 
Essays on Style, Construction, Landscape Gardening, Furniture, etc., 
etc. Illustrated by upwards of 200 engravings. By Samuel Sloan, 
Architect. 8vo $3-$° 

SLOANE. — Home Experiments in Science. 

By T. O'Conor Sloane, E. M., A.M., Ph.D. Illustrated by 91 
engravings. i2mo. ....... $1.50 

SMEATON.— Builder's Pocket-Companion : 

Containing the Elements of Building, Surveying, and Architecture; 
with Practical Rules and Instructions connected with the subject. 
By A. C. Smeaton, Civil Engineer, etc. i2mo. . . #1.50 
SMITH.— A Manual of Political Economy. 
By E. Peshine Smith. A New Edition, to which is added a full 
Index. i2mo, $1 25 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 2% 

SMITH— Parks and Pleasure -Grounds: 

Or Practical Notes on Country Residences, Villas, Public Parks, and 
Gardens. By Charles H. J. Smith, Landscape Gardener and 
Garden Architect, etc., etc. l2mo. .... $2.00 

SMITH.— The Dyer's Instructor: 

Comprising Practical Instructions in the Art of Dyeing Silk, Cotton, 
Wool, and Worsted, and Woolen Goods ; containing nearly 800 
Receipts. To which is added a Treatise on the Art of Padding; and, 
the Printing of Silk Warps, Skeins, and Handkerchiefs, and the 
various Mordants and Colors for the different styles of such work. 
By David Smith, Pattern Dyer. i2mo. . . . $2.00 

SMYTH. — A Rudimentary Treatise on Coal and Coal-Mining. 
By Warrington W. Smyth, M. A., F. R. G., President R. G. S, 
of Cornwall. Fifth editi'on, revised and corrected. With iiumer- 
ous illustrations. i2mo. . . . . . . $ r «7S 

SNIVELY.— Tables for Systematic Qualitative Chemical Anak 
ysis. 
By John H. Snively, Phr. D. 8vo. . . . . $1.00 

SNIVELY.— The Elements of Systematic Qualitative Chemical 
Analysis : 
A Hand-book for Beginners. By John H. Snively, Phr. D. i6mo. 

$2.00 

STEWART.— The American System : 

Speeches on the Tariff Question, and on Internal Improvements, 
principally delivered in the House of Representatives of the United 
States. By Andrew Stewart, late M. C. from Pennsylvania. 
With a Portrait, and a Biographical Sketch. 8vo. . . $3-O0 

STOKES. — The Cabinet-Maker and Upholsterer's Companion : 
Comprising the Art of Drawing, as applicable to Cabinet Work; 
Veneering, Inlaying, and Buhl- Work ; the Art of Dyeing and Stain- 
ing Wood, Ivory, Bone, Tortoise-Shell, etc. Directions for Lacker- 
ing, Japanning, and Varnishing; to make French Polish, Glues, 
Cements, and Composia / "ns; with numerous Receipts, useful to work 
men generally. Bv Stokes. Illustrated. A New Edition, with 
an Appendix upor /ench Polishing, Staining, Imitating, Varnishing, 
etc., etc i2mo #1.25 

STRENGTH AND OTHER PROPERTIES OF METALS; 
Reports of Experiments on the Strength and other Properties of 
Metals for Cannon. With a Description of the Machines for Testing 
Metals, and of the Classification of Cannon in service. By Officers 
of the Ordnance Department, U. S. Army. By authority of the Secre. 
taryofWar. Illustrated by 25 large steel plates. Quarto . $10.00 

SULLIVAN.— Protection to Native Industry. 

By Sir Edward Sullivan, Baronet, author of " Ten Chapters on 
Social Reforms." 8vo $1.^3 

SULZ— A Treatise on Beverages : 

Or the Complete Practical Bottler. Full instructions for Laboratory 
Work, with Original Practical Recipes for all kinds of Carbonated 
Drinks, Mineral Waters, Flavorings, Extracts, Syrups, etc. By 
Chas. Herman Sulz, Technical Chemist and Practical Bottler 
Illustrated by 428 Engravings. 818 pp. $vo. . . #10.00 



t6 HENRY CAREY BAIRu & CO.'S CATALOGUE. 

SYME. — Outlines of an Industrial Science. 
By David Syme. i2mo. . ... $2.oa 

TABLES SHOWING THE WEIGHT OF ROUND, 
SQUARE, AND FLAT BAR IRON, STEEL, ETC., 
By Measurement. Cloth ...... 6j 

TAYLOR.— Statistics of Coal : 
Including Mineral Bituminous Substances employed in Arts and 
Manufactures ; with their Geographical, Geological, and Commercial 
Distribution and Amount of Production and Consumption on the 
American Continent. With Incidental Statistics of the Iron Manu- 
facture. By R. C. Taylor. Second edition, revised by S. S. Halde- 
MAN. Illustrated by five Maps and many wood engravings. 8vo., 
cloth $10.00 

TEMPLETON. — The Practical Examinator on Steam and the 
Steam -Engine: 
With Instructive References relative thereto, arranged for the Use of 
Engineers, Students, and others. By William Templeton, En- 
gineer. i2mo. $1.25 

THAUSING.— The Theory and Practice of the Preparation of 
Malt and the Fabrication of Beer: 
With especial reference to the Vienna Process of Brewing. Elab- 
orated from personal experience by JuLius E. Thausing, Professor 
at the School for Brewers, and at the Agricultural Institute, Modling, 
near Vienna. Translated from the German by William T. Brannt, 
Thoroughly and elaborately edited, with much American matter, and 
according to the latest and most Scientific Practice, by A. Schwarz 
and Dr. A. H. Bauer. Illustrated by 140 Engravings. 8vo., 815 
pages .......... $10.00 

THOMAS.— The Modern Practice of Photography: 

By R. W. Thomas, F. C. S. 8vo. . . 75 

THOMPSON.— Political Economy. With Especial Reference 
to the Industrial History of Nations : 
By Robert E. Thompson, M. A., Professor of Social Science in the 
University of Pennsylvania. l2mo. .... $1.50 

THOMSON.— Freight Charges Calculator: 

By Andrew Thomson, Freight Agent. 2q.mo. . . $1.25 
URNER'S (THE) COMPANION: 

Containing Instructions in Concentric, Elliptic, and Eccentric Turn* 
ing; also various Plates of Chucks, Tools, and Instruments; and 
Directions for using the Eccentric Cutter, Drill, Vertical Cutter, and 
Circular Rest; with Patterns and Instructions for working them. 
J2mo. #1.25 

TURNING : Specimens of Fancy Turning Executed on the 

Hand or Foot- Lathe : 

With Geometric, Oval, and Eccentric Chucks, and Elliptical Cutting 

Frame. By an Amateur. Illustrated by 30 exquisite Photographs. 

4to. #3.00 

CRBIN— BRULL.— A Practical Guide for Puddling Iron and 
Steel. 
By Ed. Urbin, Engineer of Arts and Manufactures. A Prize Essay, 



HEKRY CAREY SAIRD & CO.'S CATALOGUE. 



read before the Association of Engineers, Graduate of the School of 
Mines, of Liege, Belgium, at the Meeting of 1865-6. To which is 
added A Comparison of the Resisting Properties of Iron and 
Steel. By A. Brull. Translated from the French by A. A. Fes- 
QUET, Chemist and Engineer. 8vo. . . . . $1.00 

VAILE. — Galvanized- Iron Cornice-Worker's Manual: 

Containing Instructions in Laying out the Different Mitres, and 
Making Patterns for all kinds of Plain and Circular Work. Also v 
Tables of Weights, Areas and Circumferences of Circles, and other 
Matter calculated to Benefit the Trade. By Charles A. Vaile. 
Illustrated by twenty-one plates. 4to $5 .00 

VILLE.— On Artificial Manures: 

Their Chemical Selection and Scientific Application to Agriculture. 
A series of Lectures given at the Experimental Farm at Vincennes, 
during 1867 and 1874-75. By M. Georges Ville. Translated and 
Edited by William Crookes, F. R. S. Illustrated by thirty-one 
engravings. 8vo., 450 pages ...... $6.00 

PILLE.— The School of Chemical Manures : 
Or, Elementary Principles in the Use of Fertilizing Agents. From 
the French of M. Geo. Ville, by A. A. Fesquet, Chemist and En- 
gineer. With Illustrations. i2mo. .... #1.25 

VOGDES.— The Architect's and Builder's Pocket- Companion 
and Price-Book : 
Consisting of a Short but Comprehensive Epitome of Decimals, Duo- 
decimals, Geometry and Mensuration ; with Tables of United States 
Measures, Sizes, Weights, Strengths, etc., of Iron, Wood, Stone, 
Brick, Cement and Concretes, Quantities of Materials in given Sizes 
and Dimensions of Wood, Brick and Stone; and full and complete 
Bibs of Prices for Carpenter's Work and Painting ; also, Rules for 
Computing and Valuing Brick and Brick Work, Stone Work, Paint- 
ing, Plastering, with a Vocabulary of Technical Terms, etc. By 
Frank W. Vogdes, Architect, Indianapolis, Ind. Enlarged, revised, 
and corrected. In one volume, 368 pages, full-bound, pocket-book 

form, gilt edges #2.00 

Cloth . . 1.5a 

^VAHL. — Galvanoplastic Manipulations : 

A Practical Guide tor the Gold and Silver Electroplater and the Gal- 
vanoplastic Operator. Comprising the Electro-Deposition of all 
Metals by means of the Battery and the Dynamo-Electric Machine, 
as well as the most approved Processes of Deposition by Simple Im- 
mersion, with Descriptions of Apparatus, Chemical Products employed 
in the Art, etc. Based largely on the " Manipulations Hydroplas- 
tiques" of Alfred Roseleur. By William H. Wahl, Ph. D. 
( Heid), Secretary of the Franklin Institute. Illustrated by 189 en- 
gravings. 8vo., 656 pages 

WALTON. — Coal-Mining Described and Illustrated: 
By Thomas H. Walton, Mining Engineer. Illustrated by 24 large 
and elaborate Plates, after Actual Workings and Apparatus. #5.00 



*8 HENRY CAREY BAIRD & CO.'S CATALOGUE. 

WARE.— The Sugar Beet. 

\ Including a History of the Beet Sugar Industry in Europe, Varieties 
of the Sugar Beet, Examination, Soils, Tillage, Seeds and Sowings 
Yield and Cost of Cultivation, Harvesting, Transportation, Conserva* 
tion, Feeding Qualities of the Beet and of the Pulp, etc. By Lewi? 
S. Ware, C. E., M. E. Illustrated by ninety engravings. 8vo. 

$4.00 
WARN.— The Sheet-Metal Worker's Instructor: 

For Zinc, Sheet- Iron, Copper, and Tin- Plate Workers, etc. Contain- 
ing a selection of Geometrical Problems ; also, Practical and Simple 
Rules for Describing the various Patterns required in the different 
branches of the above Trades. By Reuben H. Warn, Practical 
Tin- Plate Worker. To which is added an Appendix, containing 
Instructions for Boiler-Making, Mensuration of Surfaces and Solids, 
Rules for Calculating the Weights of different Figures of Iron and 
Steel, Tables of the Weights of Iron, Steel, etc. Illustrated by thirty- 
two Plates and thirty-seven Wood Engravings. 8vo. . $3.00 

WARNER.— New Theorems, Tables, and Diagrams, for the 
Computation of Earth-work : 

Designed for the use of Engineers in Preliminary and Final Estimates^ 
of Students in Engineering, and of Contractors and other non-profes. 
sional Computers. In two parts, with an Appendix. Part I. A Prac- 
tical Treatise; Part II. A Theoretical Treatise, and the Appendix. 
Containing Notes to the Rules and Examples of Part I. ; Explana- 
tions of the Construction of Scales, Tables, and Diagrams, and a 
Treatise upon Equivalent Square Bases and Equivalent Level Heights. 
The whole illustrated by numerous original engravings, comprising 
explanatory cuts for Definitions and Problems, Stereometric Scales 
and Diagrams, and a series of Lithographic Drawings from Models : 
Showing all the Combinations of Solid Forms which occur in Railroad 
Excavations and Embankments. By John Warner, A. M., Mining 
and Mechanical Engineer. Illustrated by 14 Plates. A new, revised 
and improved edition. 8vo. ...... #4.00 

WATSON.— A Manual of the Hand-Lathe : 

Comprising Concise Directions for Working Metals of all kinds, 
Ivory, Bone and Precious Woods ; Dyeing, Coloring, and French 
Polishing; Inlaying by Veneers, and various methods practised to 
produce Elaborate work with Dispatch, and at Small Expense. By 
Egbert P. Watson, Author of " The Modern Practice of American 
Machinists and Engineers." Illustrated by 78 engravings. #1,50 

WATSON. — The Modern Practice of American Machinists and 
Engineers : 

Including the Construction, Application, and Use of Drills, Lathe 
Tools, Cutters for Boring Cylinders, and Hollow-work generally, with 
the most Economical Speed for the same ; the Results verified by 
Actual Practice at the Lathe, the Vise, and on the Floor. Together 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 29 

with Workshop Management, Economy of Manufacture, the Steam- 
Engine, Bfliltrs, Gears, Belting, etc., etc. By Egbert P. Watson. 
Illustrated by eighty-six engravings. i2mo. . . . #2.50 

.VATSON.— The Theory and Practice of the Art of Weaving 
by Hand and Power : 
With Calculations and Tables for the Use of those connected with the 
Trade. By John Watson, Manufacturer and Practical Machine- 
Maker. Illustrated by large Drawings of the best Power Looms. 
8vo. .......... #7.50 

WATT.— The Art of Soap Making : 
A Practical Hand-book of the Manufacture of Hard and Soft Soaps, 
Toilet Soaps, etc., including many New Processes, and a Chapter on 
the Recovery of Glycerine from Waste Leys. By Alexander 
Watt. 111. i2mo. $3.00 

WEATHERLY.— Treatise on the Art of Boiling Sugar, Crys- 
tallizing, Lozenge-making, Comfits, Gum Goods, 

And other processes for Confectionery, etc., in which are explained, 
in an easy and familiar manner, the various Methods of Manufactur. 
ing every Description of Raw and Refined Sugar Goods, as sold by 
Confectioners and others. l2mo $l-S° 

WIGHTWICK.— Hints to Young Architects: 
Comprising Advice to those who, while yet at school, are destined 
to the Profession; to such as, having passed their pupilage, aft about 
to travel ; and to those who, having completed their education, are 
about to practise. Together with a Model Specification involvir.g a 
great variety of instructive and suggestive matter. By GeorgB 
Wightwick, Architect. A new edition, revised and considerably 
enlarged; comprising Treatises on the Principles of Construction 
and Design. By G. Huskisson Guillaume, Architect. Numerous 
illustrations. One vol. i2mo #2.00 

IVILL..— Tables of Qualitative Chemical Analysis. 
With an Introductory Chapter on the Course of Analysis. By Pro* 
essor Heinrich Will, of Giessen, Germany. Third American* 
from the eleventh German edition. Edited by Charles F. Himes* 
Ph. D., Professor of Natural Science, Dickinson College, Carlisle, Pa. 
8vo. . . • $i-$<3 

WILLIAMS.— On Heat and Steam: 
Embracing New Views of Vaporization, Condensation, and Explo- 
sion. By Charles Wye Williams, A. I. C. E. Illustrated 8vo. 

WILSON.— A Treatise on Steam Boilers : 

Their Strength, Construction, and Economical Working. By RoBERt 
Wilson. Illustrated i2mo. . . ... #2.oc 

WILSON.— First Principles of Political Economy: 
With Reference to Statesmanship and the Progress of Civilization. 
Bv Professor W. D. Wilson, of the Cornell University. A new and 
revised edition. i2mo. . . . . . . . #1.50 



30 HENRY CAREY BAIRD & CO.'S CATALOGUE. 

__ — _ i— « 

WOHLER. — A Hand-Book of Mineral Analysis : 

By F. Wohler, Professor of Chemistry in the University of GSttin* 
gen. Edited by HENRY B. Nason, Professor of Chemistry in the 
Renssalaer Polytechnic Institute, Troy, New York. Illustrated. 
I2mo . . #3.00 

WORSSAM. — On Mechanical Saws: 

From the Transactions of the Society of Engineers. 1 869. By S. W. 
Worssam, Jr. Illustrated by eighteen large plates. 8vo. #2.50 



RECENT ADDITIONS. 

ANDERSON.— The Prospector's Hand-Book: 

A Guide for the Prospector and Traveler in Search of Metal Bearing 
or other Valuable Minerals. By J. W. Anderson. 52 Illustrations. 
!2mo #1.50 

BEAUMONT.— Woollen and Worsted Cloth Manufacture: 

Being a Practical Treatise for the use of all persons employed in the 
manipulation of Textile Fabrics. By Robert Beaumont, M. S. A. 
With over 200 illustrations, including Sketches of Machinery, 
Designs, Cloths, etc. 391 pp. i2mo $2.50 

BRANNT.— The Metallic Alloys : 

A Practical Guide for the Manufacture of all kinds of Alloys, Amal* 
gams and Solders used by Metal Workers, especially by Bell Founders, 
Bronze Workers, Tinsmiths, Gold and Silver Workers, Dentists, etc., 
etc., as well as their Chemical and Physical Properties. Edited 
chiefly from the German of A. Krupp and Andreas Wildberger, with 
additions by Wm. T. Brannt. Illustrated. l2mo. $2.50 

BRANNT.— A Practical Treatise on the Manufacture of Vine- 
gar and Acetates, Cider, and Fruit- Wines : 
Preservation of Fruits and Vegetables by Canning and Evaporation ; 
Preparation of Fruit-Butters, Jellies, Marmalades, Catchups, Pickles, 
Mustards, etc. Edited from various sources. By William T. 
Brannt. Illustrated by 79 Engravings. 479 pp. 8vo. $5.00 

BRANNT.— The Metal Worker's Handy-Book of Receipts 
and Processes : 

Being a Collection of Chemical Formulas and Practical Manipula- 
tions for the working of all Metals ; including the Decoration and 
Beautifying of Articles Manufactured therefrom, as well as their 
Preservation. Edited from various sources. By William T. 
Brannt. Illustrated. i2mo. $2,50 



HENRY CAREY BAIRD & CO.'S CATALOGUE- 31 



DAVIS. A Practical Treatise on the Manufacture of Bricks, 

Tiles, Terra-Cotta, etc.: 

Including Hand-Made, Dry Clay, Tempered Clay, Soft-Mud, and 
Stiff-Clay Bricks, also Front, Hand-Pressed, Steam-Pressed, Re- 
pressed, Ornamentally Shaped and Enamelled Bricks, Drain Tiles, 
Straight and Curved Sewer and Water-Pipes, Fire-Clays, Fire-Bricks, 
Glass Pots, Terra-Cotta, Roofing Tiles, Flooring Tiles, Art Tiles, 
etc. By Charles Thomas Davis. Second Edition. 217 Engrav- 
ings. 501 pp. 8vo $5.00. 

EDWARDS. — American Marine Engineer, Theoretical and 
Practical : 
With Examples of the latest and most approved American Practice. 
By Emory Edwards. 85 illustrations. i2mo. . . $2.50 

EDWARDS. — 600 Examination Questions and Answers: 

For Engineers and Firemen (Land and Marine) who desire to ob- 
tain a United States Government or State License. Pocket-book 
form, gilt edge ........ $i-5° 

POSSELT.— Technology of Textile Design : 

Being a Practical Treatise on the Construction and Application of 
Weaves for all Textile Fabrics, with minute reference to the latest 
Inventions for Weaving. Containing also an Appendix, showing 
the Analysis and giving the Calculations necessary for the Manufac- 
ture of the various Textile Fabrics. By E. A. Posselt, Head 
Master Textile Department, Pennsylvania Museum and School of 
Industrial Art, Philadelphia, with over 1000 illustrations. 29a 
pages. 4to #5-°° 

POSSELT.— -The Jacquard Machine Analysed and Explained: 

With an Appendix on the Preparation of Jacquard Cards, and 
Practical Hints to Learners of Jacquard Designing. By E. A. 
Posselt. With 230 illustrations and numerous diagrams. 127 pp. 
4to $3-O0 

RICH.— Artistic Horse-Shoeing: 

A Practical and Scientific Treatise, giving Improved Methods of 
Shoeing, with Special Directions for Shaping Shoes to Cure Different 
Diseases of the Foot, and for the Correction of Faulty Action in 
Trotters. By George E- Rich. 62 Illustrations. 153 pages. 
i2mo. .... ..... #1.00 

RICHARDSON.— Practical Blacksmithing : 

A Collection of Articles Contributed at Different Times by Skilled 
Workmen to the columns of " The Blacksmith and Wheelwright," 
and Covering nearly the Whole Range of Blacksmithing, from the 
Simplest Job of Work to some of the Most Complex Forgings. 
Compiled and Edited by M. T. Richardson. 
Vol.1. 210 Illustrations. 224 pp. i2mo. . . , $1.00 
Vol. il. 230 Illustrations. 262 pages. 12010. . • $1,00 



32 HENRY CAREY BAIRD & CO.'S CATALOGUE. 



RICHARDSON.— The Practical Horseshoer: 

Being a Collection of Articles on Horseshoeing in all its Branchet 
which have appeared from time to time in the columns of " The 
Blacksmith and Wheelwright," etc. Compiled and edited by M. T. 
Richardson. 174 illustrations. . . . . . $1.00 

ROPER. — Instructions and Suggestions for Engineers and 
Firemen : 
By Stephen Roper, Engineer. i8mo. Morocco . #2.00 

ROPER.— The Steam Boiler: Its Care and Management: 
By Stephen Roper, Engineer. i2mo., tuck, gilt edges. $2.00 

ROPER.— The Young Engineer's Own Book: 

Containing an Explanation of the Principle and Theories on which 
the Steam Engine as a Prime Mover is Based. By Stephen Roper, 
Engineer. 160 illustrations, 363 pages. i8mo., tuck . #3.00 

ROSE. — Modern Steam- Engines: 
An Elementary Treatise upon the Steam-Engine, written in Plain 
language ; for Use in the Workshop as well as in the Drawing Office. 
Giving Full Explanations of the Construction of Modern Stearrv 
Engines : Including Diagrams showing their Actual operation. To- 
gether with Complete but Simple Explanations of the operations of 
Various Kinds of Valves, Valve Motions, and Link Motions, etc., 
thereby Enabling the Ordinary Engineer to clearly Understand the 
Principles Involved in their Construction and Use, and to Plot out 
their Movements upon the Drawing Board. By Joshua Rose. M. E. 
Illustrated by 422 engravings. 4to., 320 pages . . #6.00 

ROSE.— Steam Boilers: 

A Practical Treatise on Boiler Construction and Examination, for the 
Use of Practical Boiler Makers, Boiler Users, and Inspectors; and 
embracing in plain figures all the calculations necessary in Designing 
or Classifying Steam Boilers. By Joshua Rose, M. E. Illustrated 
by 73 engravings. 250 pages. 8vo. . . . $2.50 

SCHRIBER — The Complete Carriage and Wagon Painter: 
A Concise Compendium of the Art of Painting Carriages, Wagons, 
and Sleighs, embracing Full Directions in all the Various Branches, 
including Lettering, Scrolling, Ornamenting, Striping, Varnishing, 
and Coloring, with numerous Recipes for Mixing Colors. 73 Illus- 
trations. 177 pp. i2mo $1.00 

VAN CLEVE. — The English and American Mechanic : 

Comprising a Collection of Over Three Thousand Receipts, Rules, 
and Tables, designed for the Use of every Mechanic and Manufac- 
turer. By B. Frank Van Cleve. Illustrated. 500 pp. i2mo. #2.00 

WAHNSCHAFFE.— Guide for the Scientific Examination of 

the Soil : 

By Dr. Felix Wahnschaffe. Translated from the German by 

William T. Brannt. Illustrated by numerous Engravings. 8v % 

[In preparation. J ■* 







in. 

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